SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

SilverBox Corp IV

(Name of Issuer)

Common Shares

(Title of Class of Securities)

G81354105

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No.

G81354105

Names of Reporting Persons

Mizuho Financial Group, Inc.

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

JAPAN

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,645,673.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,645,673.00
8	Shared Dispositive Power 0.00

Aggregate Amount Beneficially Owned by Each Reporting Person

1,645,673.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

8.0 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: Mizuho Financial Group, Inc., Mizuho Bank, Ltd. and Mizuho Americas LLC may be deemed to be indirect beneficial owners of said equity securities directly held by Mizuho Securities USA LLC which is their wholly-owned subsidiary.

SCHEDULE 13G

Item 1.

(a)

Name of issuer:

SilverBox Corp IV

(b)

Address of issuer's principal executive offices:

8701 BEE CAVE ROAD, EAST BUILDING, SUITE 310, AUSTIN, TX 78746

Item 2.

(a)

Name of person filing:

Mizuho Financial Group, Inc.

(b)

Address or principal business office or, if none, residence:

1-5-5, Otemachi, Chiyoda-ku, Tokyo, 100-8176, Japan

(c)

Citizenship:

Japan

(d)

Title of class of securities:

Common Shares

(e)

CUSIP No.:

G81354105

Item 3.

If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b)

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c)

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d)

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e)

An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f)

An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g)

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:

(k)

Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

Parent Holding Company

Item 4.

Ownership

(a)

Amount beneficially owned:

1,645,673

(b)

Percent of class:

8.0 %

(c)

Number of shares as to which the person has:

(i) Sole power to vote or to direct the vote:

1,645,673

(ii) Shared power to vote or to direct the vote:

(iii) Sole power to dispose or to direct the disposition of:

1,645,673

(iv) Shared power to dispose or to direct the disposition of:

Item 5.

Ownership of 5 Percent or Less of a Class.

Not Applicable

Item 6.

Ownership of more than 5 Percent on Behalf of Another Person.

Not Applicable

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary.

See Exhibit A

Item 8.

Identification and Classification of Members of the Group.

Not Applicable

Item 9.

Notice of Dissolution of Group.

Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11. By signing below I certify that, to the best of my knowledge and belief, the foreign regulatory scheme applicable to Parent Holding Company is substantially comparable to the regulatory scheme applicable to the functionally equivalent U.S. institution(s). I also undertake to furnish to the Commission staff, upon request, information that would otherwise be disclosed in a Schedule 13D.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Mizuho Financial Group, Inc.

Signature:	/s/ Takahiro Katsura
Name/Title:	Takahiro Katsura, Managing Director, Global Corporate Function Coordination Department
Date:	02/12/2026

SEC Form SCHEDULE 13G filed by SilverBox Corp IV