EX-10.5





 Exhibit 10.5 

November 9, 2021 
 Blockchain Coinvestors
Acquisition Corp. I 
 PO Box 1093, Boundary Hall 
 Cricket
Square, Grand Cayman 
 KY1-1102, Cayman Islands 

Re: Initial Public Offering 
 Ladies and
Gentlemen: 
 This letter (this “Letter Agreement”) is being delivered to you in accordance with the Underwriting Agreement (the
“Underwriting Agreement”) entered into by and among Blockchain Coinvestors Acquisition Corp. I, a Cayman Islands exempted company (the “Company”) and Cantor Fitzgerald & Co. and
Moelis & Company, as representatives (the “Representatives”) of the several underwriters (the “Underwriters”), relating to an underwritten initial public offering (the “Public
Offering”) of 30,015,000 of the Company’s units (including up to 3,915,000 units that may be purchased pursuant to the Underwriters’ option to purchase additional units, the “Units”), each comprising
one of the Company’s Class A ordinary shares, par value $0.0001 per share (the “Ordinary Shares”), and one-half of one redeemable warrant (each whole warrant, a
“Warrant”). Each Warrant entitles the holder thereof to purchase one Ordinary Share at a price of $11.50 per share, subject to adjustment. The Units will be sold in the Public Offering pursuant to a registration statement on
Form S-1 and a prospectus (the “Prospectus”) filed by the Company with the U.S. Securities and Exchange Commission (the “Commission”). Certain capitalized terms
used herein are defined in paragraph 1 hereof. 
 In order to induce the Company and the Underwriters to enter into the Underwriting Agreement and to
proceed with the Public Offering and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, Blockchain Coinvestors Acquisition Sponsors I LLC (the “Sponsor) and each of the
undersigned (each, an “Insider” and collectively, the “Insiders”) hereby agree with the Company as follows: 

1. Definitions. As used herein, (i) “Business Combination” shall mean a merger, share exchange, asset
acquisition, share purchase, reorganization or similar business combination with one or more businesses or entities; (ii) “Founder Shares” shall mean the 10,005,000 Class B ordinary shares of the Company, par value
$0.00009 per share, outstanding prior to the consummation of the Public Offering; (iii) “Private Placement Units” shall mean the units of the Company that will be acquired by the Sponsor for an aggregate purchase price of
$12,440,000 (or up to $13,223,000 if the Underwriters exercise their option to purchase additional units), or $10.00 per Unit, in a private placement that shall close simultaneously with the consummation of the Public Offering; (iv)
“Public Shareholders” shall mean the holders of Ordinary Shares included in the Units issued in the Public Offering; (v) “Public Shares” shall mean the Ordinary Shares included in the Units issued in
the Public Offering; (vi) “Trust Account” shall mean the trust account into which a portion of the net proceeds of the Public Offering and the sale of the Private Placement Units shall be deposited; (vii)
“Transfer” shall mean the (a) sale of, offer to sell, contract or agreement to sell, hypothecate, pledge, grant of any option to purchase or otherwise dispose of or agreement to dispose of, directly or indirectly, or
establishment or increase of a put equivalent position or liquidation with respect to or decrease of a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, and the rules and regulations
of the Commission promulgated thereunder with respect to, any security, (b) entry into any swap or other arrangement that transfers to another, in whole or in part, any of the economic consequences of ownership of any security, whether any such
transaction is to be settled by delivery of such securities, in cash or otherwise, or (c) public announcement of any intention to effect any transaction specified in clause (a) or (b); and (viii) “Charter” shall
mean the Company’s Amended and Restated Memorandum and Articles of Association, as the same may be amended from time to time. 












 2. Representations and Warranties. 

(a) The Sponsor and each Insider, with respect to itself, herself or himself, represent and warrant to the Company that it, she or he has the
full right and power, without violating any agreement to which it, she or he is bound (including, without limitation, any non-competition or non-solicitation agreement
with any employer or former employer), to enter into this Letter Agreement, as applicable, and to serve as an officer of the Company and/or a director on the Company’s Board of Directors (the “Board”), as applicable, and
each Insider hereby consents to being named in the Prospectus, road show and any other materials as an officer and/or director of the Company, as applicable. 

(b) Each Insider represents and warrants, with respect to herself or himself, that such Insider’s biographical information furnished to
the Company (including any such information included in the Prospectus) is true and accurate in all material respects and does not omit any material information with respect to such Insider’s background. The Insider’s questionnaire
furnished to the Company is true and accurate in all material respects. Each Insider represents and warrants that such Insider is not subject to or a respondent in any legal action for, any injunction, cease-and-desist order or order or stipulation to desist or refrain from any act or practice relating to the offering of securities in any jurisdiction; such Insider has never been convicted of, or pleaded
guilty to, any crime (i) involving fraud, (ii) relating to any financial transaction or handling of funds of another person, or (iii) pertaining to any dealings in any securities and such Insider is not currently a defendant in any
such criminal proceeding; and such Insider has never been suspended or expelled from membership in any securities or commodities exchange or association or had a securities or commodities license or registration denied, suspended or revoked. 

3. Business Combination Vote. It is acknowledged and agreed that the Company shall not enter into a definitive agreement regarding a
proposed Business Combination without the prior consent of the Sponsor. The Sponsor and each Insider, with respect to itself or herself or himself, agrees that if the Company seeks shareholder approval of a proposed initial Business Combination,
then in connection with such proposed initial Business Combination, it, she or he, as applicable, shall vote all Founder Shares and any Public Shares held by it, her or him, as applicable, in favor of such proposed initial Business Combination
(including any proposals recommended by the Board in connection with such Business Combination) and not redeem any Public Shares held by it, her or him, as applicable, in connection with such shareholder approval. 

4. Failure to Consummate a Business Combination; Trust Account Waiver. 

(a) The Sponsor and each Insider hereby agree, with respect to itself, herself or himself, that in the event that the Company fails to
consummate its initial Business Combination within the time period set forth in the Charter, the Sponsor and each Insider shall take all reasonable steps to cause the Company to (i) cease all operations except for the purpose of winding up;
(ii) as promptly as reasonably possible but not more than 10 business days thereafter, redeem 100% of the Public Shares, at a per-share price, payable in cash, equal to the aggregate amount then on
deposit in the Trust Account, including interest earned on the funds held in the Trust Account and not previously released to the Company to pay income taxes (less up to $100,000 of interest to pay dissolution expenses), divided by the number of
then outstanding Public Shares, which redemption will completely extinguish Public Shareholders’ rights as shareholders (including the right to receive further liquidation distributions, if any); and (iii) as promptly as reasonably
possible following such redemption, subject to the approval of the Company’s remaining shareholders and the Board, liquidate and dissolve, subject in the case of clauses (ii) and (iii) to the Company’s obligations under Cayman Islands
law to provide for claims of creditors and in all cases subject to the other requirements of applicable law. The Sponsor and each Insider agree not to propose any amendment to the Charter (i) that would modify the substance or timing of the
Company’s obligation to provide holders of the Public Shares the right to have their shares redeemed in connection with an initial Business Combination or to redeem 100% of the Public Shares if the Company does not complete an initial Business
Combination within the required time period set forth in the Charter or (ii) with respect to any provision relating to the rights of holders of Public Shares unless the Company provides its Public Shareholders with the opportunity to redeem
their Public Shares upon approval of any such amendment at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account, including interest earned on the funds held in
the Trust Account and not previously released to the Company to pay taxes, if any, divided by the number of then-outstanding Public Shares. 












 (b) The Sponsor and each Insider, with respect to itself, herself or himself, acknowledges
that it, she or he has no right, title, interest or claim of any kind in or to any monies held in the Trust Account or any other asset of the Company as a result of any liquidation of the Company with respect to the Founder Shares held by it, her or
him, if any. The Sponsor and each of the Insiders hereby further waive, with respect to any Founder Shares and Public Shares held by it, her or him, as applicable, any redemption rights it, she or he may have in connection with the consummation of a
Business Combination, including, without limitation, any such rights available in the context of a shareholder vote to approve such Business Combination or a shareholder vote to approve an amendment to the Charter (i) that would modify the
substance or timing of the Company’s obligation to provide holders of the Public Shares the right to have their shares redeemed in connection with an initial Business Combination or to redeem 100% of the Public Shares if the Company has not
consummated an initial Business Combination within the time period set forth in the Charter or (ii) with respect to any provision relating to the rights of holders of Public Shares (although the Sponsor and the Insiders shall be entitled to
liquidation rights with respect to any Public Shares they hold if the Company fails to consummate a Business Combination within the required time period set forth in the Charter). 

5. Lock-up; Transfer Restrictions. 

(a) The Sponsor and the Insiders agree that the Insider shall not Transfer any Founder Shares (the “Founder Shares Lock-up”) until the earliest of (A) one year after the completion of our initial business combination and (B) subsequent to our initial business combination, (x) if the closing price of
our Class A ordinary shares equals or exceeds $12.00 per share (as adjusted for share subdivisions, share capitalizations, reorganizations, recapitalizations and the like) for any 20 trading days within any
30-trading day period commencing at least 150 days after our initial business combination, or (y) the date on which we complete a liquidation, merger, share exchange or other similar transaction that
results in all of our public shareholders having the right to exchange their ordinary shares for cash, securities or other property. (the “Founder Shares Lock-up Period”). 

(b) The Sponsor and Insiders agree that they shall not effectuate any Transfer of Private Placement Units or the securities within the Private
Placement Units until 30 days after the completion of an initial Business Combination. 
 (c) Notwithstanding the provisions set forth in
paragraphs 5(a) and (b), Transfers of the Founder Shares, Private Placement Units and the securities within the Private Placement Units are permitted (a) to the Company’s officers or directors, any affiliate or family member
of any of the Company’s officers or directors, any members or partners of the Sponsor or their affiliates, any affiliates of the Sponsor, or any employees of such affiliates; (b) in the case of an individual, by gift to a member of one of
the individual’s immediate family or to a trust, the beneficiary of which is a member of the individual’s immediate family, an affiliate of such person or to a charitable organization; (c) in the case of an individual, by virtue of
laws of descent and distribution upon death of the individual; (d) in the case of an individual, pursuant to a qualified domestic relations order; (e) by private sales or transfers made in connection with any forward purchase agreement or
similar arrangement or in connection with the consummation of a Business Combination at prices no greater than the price at which the Founder Shares, Private Placement Units or Ordinary Shares, as applicable, were originally purchased; (f) by
virtue of the Sponsor’s organizational documents upon liquidation or dissolution of the Sponsor; (g) to the Company for no value for cancellation in connection with the consummation of an initial Business Combination, (h) in the event
of the Company’s liquidation prior to the completion of a Business Combination; or (i) in the event of completion of a liquidation, merger, share exchange or other similar transaction which results in all of the Company’s Public
Shareholders having the right to exchange their Ordinary Shares for cash, securities or other property subsequent to the completion of an initial Business Combination; provided, however, that in the case of clauses (a) through (f)
these permitted transferees must enter into a written agreement agreeing to be bound by these transfer restrictions. 
 (d) During the
period commencing on the effective date of the Underwriting Agreement and ending 180 days after such date, the Sponsor and each Insider shall not, without the prior written consent of the Representatives, Transfer any Units, Ordinary Shares,
Warrants or any other securities convertible into, or exercisable or exchangeable for, Ordinary Shares held by it, her or him, as applicable, subject to certain exceptions set forth in the Underwriting Agreement. 












 6. Remedies. The Sponsor and each of the Insiders hereby agree and acknowledge that
(i) each of the Underwriters and the Company would be irreparably injured in the event of a breach by the Sponsor or such Insider of its, her or his obligations, as applicable under paragraphs 3, 4, 5, 7, 10
and 11 (ii) monetary damages may not be an adequate remedy for such breach and (iii) the non-breaching party shall be entitled to injunctive relief, in addition to any other remedy that such party
may have in law or in equity, in the event of such breach. 
 7. Payments by the Company. Except as disclosed in the Prospectus,
neither the Sponsor nor any affiliate of the Sponsor nor any director or officer of the Company nor any affiliate of the officers shall receive from the Company any finder’s fee, reimbursement, consulting fee, monies in respect of any payment
of a loan or other compensation prior to, or in connection with any services rendered in order to effectuate the consummation of the Company’s initial Business Combination (regardless of the type of transaction that it is). 

8. Director and Officer Liability Insurance. The Company will maintain an insurance policy or policies providing directors’ and
officers’ liability insurance, and the Insiders shall be covered by such policy or policies, in accordance with its or their terms, to the maximum extent of the coverage available for any of the Company’s directors or officers. 

9. Termination. This Letter Agreement shall terminate on the earlier of (i) the expiration of the Founder Shares Lock-up Period and (ii) the liquidation of the Company. 
 10. Indemnification. In the event
of the liquidation of the Trust Account upon the failure of the Company to consummate its initial Business Combination within the time period set forth in the Charter, the Sponsor (the “Indemnitor”) agrees to indemnify and
hold harmless the Company against any and all loss, liability, claim, damage and expense whatsoever (including, but not limited to, any and all legal or other expenses reasonably incurred in investigating, preparing or defending against any
litigation, whether pending or threatened) to which the Company may become subject as a result of any claim by (i) any third party for services rendered or products sold to the Company (except for the Company’s independent auditors) or
(ii) any prospective target business with which the Company has discussed entering into a transaction agreement (a “Target”); provided, however, that such indemnification of the Company by the Indemnitor (x) shall
apply only to the extent necessary to ensure that such claims by a third party for services rendered or products sold to the Company or a Target do not reduce the amount of funds in the Trust Account to below the lesser of (i) $10.00 per Public
Share and (ii) the actual amount per Public Share held in the Trust Account as of the date of the liquidation of the Trust Account if less than $10.00 per Public Share due to reductions in the value of the trust assets, in each case net of
interest that may be withdrawn to pay the Company’s tax obligations, (y) shall not apply to any claims by a third party or Target who executed a waiver of any and all rights to the monies held in the Trust Account (whether or not such
waiver is enforceable) and (z) shall not apply to any claims under the Company’s indemnity of the Underwriters against certain liabilities, including liabilities under the Securities Act of 1933, as amended. The Indemnitor shall have the
right to defend against any such claim with counsel of its choice reasonably satisfactory to the Company if, within 15 days following written receipt of notice of the claim to the Indemnitor, the Indemnitor notifies the Company in writing that it
shall undertake such defense. For the avoidance of doubt, none of the Company’s officers or directors will indemnify the Company for claims by third parties, including, without limitation, claims by vendors and prospective target businesses.

 11. Forfeiture of Founder Shares. To the extent that the Underwriters do not exercise their option to purchase additional Units
within 45 days from the date of the Prospectus in full (as further described in the Prospectus), the Sponsor agrees to automatically surrender to the Company for no consideration, for cancellation at no cost, an aggregate number of Founder Shares so
that the number of Founder Shares will equal 25% of the sum of the total number of Ordinary Shares and Founder Shares outstanding at such time. The Sponsor and Insiders further agree that to the extent that the size of the Public Offering is
increased or decreased, the Company will effect a share capitalization or a share repurchase, as applicable, with respect to the Founder Shares immediately prior to the consummation of the Public Offering in such amount as to maintain the number of
Founder Shares at 25% of the sum of the total number of Ordinary Shares and Founder Shares outstanding upon completion of the Public Offering. 

12. Entire Agreement. This Letter Agreement constitutes the entire agreement and understanding of the parties hereto in respect of the
subject matter hereof and supersedes all prior understandings, agreements, or representations by or among the parties hereto, written or oral, to the extent they relate in any way to the subject matter hereof or the transactions contemplated hereby.
This Letter Agreement may not be changed, amended, modified or waived (other than to correct a typographical error) as to any particular provision, except by a written instrument executed by all parties hereto. 












 13. Assignment. No party hereto may assign either this Letter Agreement or any of its
rights, interests, or obligations hereunder without the prior written consent of the other parties. Any purported assignment in violation of this paragraph shall be void and ineffectual and shall not operate to transfer or assign any interest or
title to the purported assignee. This Letter Agreement shall be binding on the Sponsor, each of the Insiders, and each of their respective successors, heirs, personal representatives and assigns and permitted transferees. 

14. Counterparts. This Letter Agreement may be executed in any number of original or facsimile counterparts, and each of such
counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument. 

15. Effect of Headings. The paragraph headings herein are for convenience only and are not part of this Letter Agreement and shall not
affect the interpretation thereof. 
 16. Severability. This Letter Agreement shall be deemed severable, and the invalidity or
unenforceability of any term or provision hereof shall not affect the validity or enforceability of this Letter Agreement or of any other term or provision hereof. Furthermore, in lieu of any such invalid or unenforceable term or provision, the
parties hereto intend that there shall be added as a part of this Letter Agreement a provision as similar in terms to such invalid or unenforceable provision as may be possible and be valid and enforceable. 

17. Governing Law. This Letter Agreement shall be governed by and construed and enforced in accordance with the laws of the State of
Delaware, without giving effect to conflicts of law principles that would result in the application of the substantive laws of another jurisdiction. The parties hereto (i) all agree that any action, proceeding, claim or dispute arising out of,
or relating in any way to, this Letter Agreement shall be brought and enforced only in the Court of Chancery of the State of Delaware, and irrevocably submit to such jurisdiction and venue, which jurisdiction and venue shall be exclusive, and
(ii) waive any objection to such exclusive jurisdiction and venue or that such courts represent an inconvenient forum. 
 18.
Notices. Any notice, consent or request to be given in connection with any of the terms or provisions of this Letter Agreement shall be in writing and shall be sent by express mail or similar private courier service, by certified mail (return
receipt requested), by hand delivery or facsimile or other electronic transmission. 
 [Signature Page Follows]













 
			
	Sincerely,
	
	BLOCKCHAIN COINVESTORS ACQUISITION SPONSORS I LLC
		
	By:	 	 
	Name:	 	Matthew C. Le Merle
	Title:	 	Manager
		
		 	 
		 	Matthew C. Le Merle
		
		 	 
		 	Lou Kerner
		
		 	 
		 	Alison Davis
		
		 	 
		 	Gary Cookhorn
		
		 	 
		 	Rebecca Macieira-Kaufmann
		
		 	 
		 	Colin Wiel


  

			
	Acknowledged and Agreed:
	
	BLOCKCHAIN COINVESTORS ACQUISITION CORP. 1
		
	By:	 	 
		 	Name: Lou Kerner
		 	Title: Chief Executive Officer