Exhibit 10.1

AMENDMENT TO INSIDER LETTER

THIS AMENDMENT NO. 1 to the Letter Agreement dated January 28, 2026 (the “Insider Letter”) by and between K2 Capital Acquisition Corporation (the “Company”), K2 Capital Sponsor LLC (the “Sponsor”) and the insiders signatory to the Insider Letter (the “Insiders”) is dated as of August 26, 2026 (“Amendment No. 1”). The purpose of Amendment No. 1 is to amend paragraphs 7(a) and 7(b) of the Insider Letter to amend the lock-up provisions. Terms not otherwise defined herein are as defined in the Insider Letter.

NOW, THEREFORE, THE PARTIES HERETO AGREE AS FOLLOWS:

“7. (a) The Sponsor and each Insider agree that it, he or she shall not Transfer (as defined below) any Founder Shares (or Class A Ordinary Shares issuable upon conversion thereof) until the earlier of: (i) six months after completion of the Business Combination or (ii) the closing price of the Class A Ordinary Shares equals or exceeds $12.00 per share (as adjusted for stock splits, stock dividends, reorganizations, recapitalizations and other similar transactions) for any 20 trading days within any 30-trading day period commencing at least 150 days after completion of the Business Combination (the “Lock-up”).”

“(b) The Sponsor and each Insider agree not to Transfer any Private Placement Units (including the underlying securities) held by it, he or she until 30 days after the completion of a Business Combination.”

IN WITNESS WHEREOF, the undersigned have set their hand as of the date first above written.