Company: CNCKW
Filing Date: 2025-11-12
Form Type: 6-K
Source: 0001913847-25-000023
Chunk: 0

Company: Coincheck Group N.V.
Filing Date: 2025-11-12
Form: 6-K
Chunk 0
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### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### WASHINGTON, DC 20549

#### FORM 6-K

### REPORT OF FOREIGN PRIVATE ISSUER

#### PURSUANT TO RULE 13a-16 OR 15d-16 UNDER

#### THE SECURITIES EXCHANGE ACT OF 1934

#### For the month of November 2025

#### Commission File Number: 001-42438

#### COINCHECK GROUP N.V.
<div align='center'>(Translation of registrant’s name into English)</div>

#### Nieuwezijds Voorburgwal 162

#### 1012 SJ Amsterdam

#### The Netherlands
<div align='center'>(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F:

Form 20-F ☒ Form 40-F ☐</div>

On November 12, 2025, Coincheck Group N.V. (“Coincheck Group”) issued a press release, announcing its financial results for its second quarter of the fiscal year ending March 31, 2026, which is furnished as Exhibit 99.1 to this Report on Form 6-K.

The information in this Report on Form 6-K is incorporated by reference into Coincheck Group’s Registration Statement on Form S-8 (File No. 333-286190), to the extent not superseded by documents or reports subsequently filed or furnished.

#### Exhibit Index
<div align='center'>2</div>

### SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

| Date: November 12, 2025 |     | COINCHECK GROUP N.V. 
 By:                  |     | /s/ Gary A. Simanson |     |                                       |
|:------------------------|:----|:---------------------|:----|:---------------------|:----|:--------------------------------------|
|                         |     |                      |     | Name:                |     | Gary A. Simanson                      |
|                         |     |                      |     | Title:               |     | Chief Executive Officer and President |

<div align='center'>3</div>