Document:

<PAGE>
                                                                    Exhibit 10.6

                          AMENDMENT ON LEASE AGREEMENT
                          ----------------------------

     This is an agreement (the "Agreement") between K-1 Corporate Restructuring
Real Estate Investment Trusts Company, Ltd. (the "Lessor") and WiderThan Co.,
Ltd. (the "Lessee") to amend the agreement (the "Lease Agreement") dated October
11, 2003, on leasing of K1 REIT building (463, Chungjeong-ro 3-ga, Saedaenum-go,
Seoul, Korea) (the "Leased Building") as follows.

1. Clause 1 (Specifications of the Leased Building)

The Lessor agrees to lease the Leased Building specified below to the Lessee and
Lessee agrees to lease the Leased Building from the Lessor.

<Table>
<Caption>
--------------------------------------------------------------------------------
    Address        463, Chungjeong-ro 3-ga, Saedaenum-go, Seoul, Korea
--------------------------------------------------------------------------------
<S>                <C>
  Name of the      K1 REIT Building (Previously Regent Fire & Marine Insurance
   building        Building)
--------------------------------------------------------------------------------
    Floors         5 floors (14th, 15th, 16th, 17th and 3rd floor)
--------------------------------------------------------------------------------
     Area          7,209.42 m(2) (2,180.84 pyong)        Purpose        Business
--------------------------------------------------------------------------------
 </Table>

2. Clause 3. (Leasehold deposit)

1) The Lessee agrees to deposit interest-free leasehold deposit to the Lessor as
below. Full amount must be paid before the lease period starts.

<Table>
<Caption>
--------------------------------------------------------------------------------
  Lease Deposit                     Amount                       Payment date
--------------------------------------------------------------------------------
<S>                      <C>                                    <C>
 Existing deposit        W 812,610,000                           Already paid
--------------------------------------------------------------------------------
Additional deposit       W 212,378,000                          Date of signing
--------------------------------------------------------------------------------
     Total               W 1,024,988,000
--------------------------------------------------------------------------------
</Table>
<PAGE>

3. Clause 4 (Rent)

The Lessee will pay W 102,498,000 (W 47,000 per pyong) excluding VAT(Value Added
Tax) every month to the Lessor as rent.

4. Clause 5 (Maintenance expenses)

1) The Lessee will pay W 54,520,000 (W 25,000 per pyong) excluding VAT every
month to the Lessor as fixed maintenance expenses.

5. Clause 9 (Usage of parking lots)

The Lessee can use 40 parking lots (8 per floor) for free. The Lessee agrees to
abide by the Parking Lot Management Rules set by the Lessor separately.

6. This Agreement will take effect on April 21, 2004. Additional area on the 3rd
floor will be subject to below rent and maintenance expenses.

1) Maintenance expenses for 3rd floor will be applied starting June 1, 2004.

2) Rent for 3rd floor will be applied starting July 1, 2004.

Items not discussed in this Agreement will be regulated by the original Lease
Agreement and other amendments to the Lease Agreement.
<PAGE>

In witness whereof, the undersigned, being duly authorized by their respective
Parties, have signed this agreement. This agreement is drafted and signed in
duplicate copies, both copies being equally authentic, and each copy shall be
kept by each party.

                                                                   2004. 04. 21.

<TABLE>
<S>              <C>

Lessor           Name: K-1 Corporate Restructuring Real Estate Investment
                 Trusts Company, Ltd.
                 Address: 14F/Sins Tower, 144-25 Samsung-dong, Kangnam-gu, Seoul
                 /s/ Lee, Ho-gil
                 Lee, Ho-gil, CEO
                 Corporate registration number: 110111-2616534

Lessee           Name: WiderThan Co., Ltd.
                 Address: 463 Chungjeong-ro 3-ga, Seodaemun-gu, Seoul
                 /s/ Jin Woo So
                 Jin Woo So, CEO
                 Corporate registration number: 110111-1998701
</TABLE><PAGE>
                                                                    Exhibit 10.7

                            SHARE PURCHASE AGREEMENT

By signing this contract, _____ (the "Seller") agrees to sell the shares of
WiderThan Co., Ltd. (the "Company") held by the Seller to _____ ("the
Purchaser") under the following conditions.

1 (Object)

The Seller agrees to sell ___ shares of common stock, par value Won 500 per
share of the Company (the "Shares") to the Purchaser under the conditions set
forth in this document.

2 (Purchase price)

The Shares will be purchased at a purchase price of Won 500 per share, which
aggregates to Won ___ in total (the "Purchase Price").

3 (Payment)

The Purchaser will pay the Purchase Price to the Seller no later than _____ in
cash.

4 (Transfer of shareholder name)

4.1 The Seller immediately transfers all the rights as a shareholder to the
Purchaser when the Purchase Price is paid to the Seller under the clause 3.

4.2 The Purchaser will apply for the transfer of shareholder name with the
Company and the Seller will provide necessary assistance to such process.

5 (Tax and Commissions)

All the tax and commissions including share transfer tax relating to the
agreement and execution of this contract will be respectively paid by each party
with adherence to legal obligations and liabilities.

6 (Resolution of disputes)

The Seller and the Purchaser will put their efforts to solve any dispute arising
from or in connection with this contract in an amicable manner. Any dispute,
controversy or claim not solved in [a friendly terms] will be referred to and
finally
<PAGE>

resolved under the jurisdiction of Seoul District Court.

In witness whereof, the undersigned, being duly authorized by their respective
Parties, have signed this agreement. This agreement is drafted and signed in
duplicate copies, both copies being equally authentic, and each copy shall be
kept by each party.

                                                                  Date 200 . . .

<TABLE>
<S>                                    <C>

Seller                                 Purchaser
Name                                   Name
                           (sign)                                     (Sign)
---------------------------            -------------------------------
Resident Registration Number:          Resident Registration Number:

---------------------------            -------------------------------
Address:                               Address:

---------------------------            -------------------------------
</TABLE><PAGE>
                                                                    Exhibit 10.8

                     AGREEMENT ON SHARE TRANSFER RESTRICTION

WiderThan Co., Ltd. (the "Company") and _____ (the "Shareholder") agrees on the
restriction on transfer of shares of the Company which is held by or will be
obtained by the Shareholder through right issue, bonus issue, employee share
ownership association, stock dividends, stock option and other sources not
specified (the "Shares").

     1. The Shareholder must notify and obtain approval from the Company prior
     to transfer of the Shares.

     2. The Company may provide the right of first refusal at par value to the
     Company or to a person designated by the Company on the Shares which the
     Shareholder intends to transfer, except when reason of share transfer is
     unavoidable such as inheritance.

     3. The Shareholder agrees that in case the Shareholder quits the Company
     before termination of this agreement, the Company may decide the Shares to
     be transferred to a third party at par value.

     4. This contract will be terminated 3 years after the agreement has been
     signed. However, if the Company is listed in domestic or foreign stock
     exchange before the termination, this agreement will be effective until the
     time of listing.

     5. The Shareholder will be liable for all the civil claims and liabilities
     in case the Shareholder fails to comply with the conditions set forth in
     this contract.

     In witness whereof, the undersigned, being duly authorized by their
     respective Parties, have signed this agreement. This agreement is drafted
     and signed in duplicate copies, both copies being equally authentic, and
     each copy shall be kept by each party.

                                                                         200 . .

<TABLE>
<S>                                      <C>

Company                                  Shareholder
WiderThan Co., Ltd.                      Name:
--------------------------                     -------------------------
463 Chungjeong-ro 3-ga,                  Address:
Seodaemun-gu, Seoul
WiderThan Co., Ltd.
CEO Sangjun Park
</TABLE><PAGE>
                                                                    Exhibit 10.9

                       AGREEMENT OF RIGHT OF FIRST REFUSAL

WiderThan Co., Ltd. (the "Company") and _____________ ("Shareholder") have
agreed on the conclusion of the right of first refusal of the shares of the
Company held by the Shareholder (the "Shares") as the following:

1.   Definitions

     (1)  The "Shares" refer to common shares of the Company held by the
          Shareholder.

     (2)  The "Expected Transaction Price" refers to the price at which the
          Shareholder intends to transfer the Shares to a third party.

     (3)  The "Right of First Refusal" refers to the right of the Company to
          have priority over others in purchasing the Shares held by the
          Shareholder.

2.   Scope of agreement

     (1)  In case the Shareholder intends to transfer all or a part of the
          Shares to a third party, the Shareholder must notify the Company of
          the Expected Transaction Price, transferee, and transaction timing in
          advance.

     (2)  The Company can purchase the Shares from the Shareholder or designate
          an entity to purchase the Shares at the Expected Transaction Price
          prior to purchase by any other entities.

     (3)  The Company must notify the Shareholder whether it would exercise or
          waive the right of first refusal within two weeks from the date the
          Shareholder notified the Company of the transfer of the Shares.

     (4)  In case the Company notified its willingness to exercise the Right of
          First Refusal, the Company or the entity designated by the Company
          shall immediately conclude a share purchase agreement with the
          Shareholder and make payment for the Shares.

                                       1
<PAGE>

     (5)  In case the Company waives its Right of First Refusal, the Shareholder
          should transfer to intending purchaser(s) all or a part of the Shares
          at a price no less than the Expected Transaction Price previously
          notified to the Company.

3.   Application for Shareholder name transfer

     (1)  In case the Shareholder signs a share purchase agreement with a third
          party after the Company's waiver of right of first refusal, the
          Shareholder shall submit copies of the share purchase agreement and
          payment receipt to the Company within one week of the execution of the
          agreement and receipt of the payment, and the third party shall apply
          for shareholder name transfer with the Company.

4.   Execution

     (1)  In case the Company or the Shareholder violates this agreement, the
          violating entity shall be responsible for all civil liabilities.

5.   Interpretation

Any discrepancies in interpretation of this agreement or matters not mentioned
in this agreement shall be resolved by an agreement between the Shareholder and
the Company.

6.   Effective date and termination

     This agreement shall become effective on the signing date of both parties.
     This agreement shall be terminated when the common shares of the Company
     are listed on domestic or foreign stock exchange.

7.   Confidentiality

     (1)  The Parties of the agreement shall not disclose any information

                                       2
<PAGE>

          regarding the existence of this agreement, the contents, or the share
          transaction to a third party unless it is required by the law or the
          regulatory body or a written consent is received from the other side
          of the Parties.

     (2)  In addition, during the course of share transaction, the Shareholder
          must secure insider information of the Company from the counterpart of
          the transaction or the third party.

8.   Resolution of disputes

The Parties shall make efforts to resolve any disputes related to this agreement
in an amicable manner. Unsettled disputes will be resolved under the
jurisdiction of the Seoul District Court.

In witness whereof, the undersigned, being duly authorized by their respective
Parties, have signed this agreement. This agreement is drafted and signed in
duplicate copies, both copies being equally authentic, and each copy shall be
kept by each party.

                                                                 Date: 200 . . .

<TABLE>
<S>                <C>

"The Company"
                   463 Chungjeong-ro 3-ga, Seodaemun-gu, Seoul
                   WiderThan Co., Ltd.
                   CEO Sangjun Park

"Shareholder"
                   Name:
                   Signature: ______________________
                   Address:
                   SSN:
</TABLE>

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