Form 3 Keystone Acquisition For: Jun 02 Filed by: Keystone International Acquisition Management LLC

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June 2, 2026 9:51 PM EDT
FORM 3 UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940
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1. Name and Address of Reporting Person *
Keystone International Acquisition Management LLC
(Last) (First) (Middle)
C/O KEYSTONE ACQUISITION CORP.
142 WEST 57TH STREET, 11TH FLOOR
(Street)
NEW YORK NY 10019
(City) (State) (Zip)
2. Date of Event Requiring Statement (Month/Day/Year)
06/02/2026 		3. Issuer Name and Ticker or Trading Symbol
Keystone Acquisition Corp. [ KEYY ]
4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
X Director X 10% Owner
X Officer (give title below) Other (specify below)
Executive Chairman
 5. If Amendment, Date of Original Filed (Month/Day/Year)
6. Individual or Joint/Group Filing (Check Applicable Line)
Form filed by One Reporting Person
X Form filed by More than One Reporting Person
Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5)
Table II - Derivative Securities Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4) 2. Date Exercisable and Expiration Date (Month/Day/Year) 3. Title and Amount of Securities Underlying Derivative Security (Instr. 4) 4. Conversion or Exercise Price of Derivative Security 5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 6. Nature of Indirect Beneficial Ownership (Instr. 5)
Date Exercisable Expiration Date Title Amount or Number of Shares
Class B Ordinary Shares   (1)   (1) Class A Ordinary Shares 9,483,333 (1) D (2)  
Explanation of Responses:
1. The Class B ordinary shares are convertible for the Issuer's Class A ordinary shares as described under the heading "Description of Securities" in the Issuer's Registration Statement on Form S-1 (File No. 333-295539) (the "Registration Statement") and have no expiration date. The Class B ordinary shares beneficially owned by the Reporting Persons include up to 1,250,000 Class B ordinary shares subject to forfeiture to the Issuer depending on the extent to which the underwriters' over-allotment option is exercised in connection with the Issuer's initial public offering of units, as described in the Registration Statement.
2. Keystone International Acquisition Management LLC is the record holder of the securities reported herein. Jae Hyun (James) Park is the managing member of Keystone International Acquisition Management LLC. Mr. Park has voting and investment discretion with respect to the securities held of record by Keystone International Acquisition Management LLC.
Remarks:
See Exhibit 99.1 - Joint Filer Information, which is incorporated herein by reference and describes in further detail the relationships of the Reporting Persons to the Issuer. See Exhibits 24.1 and 24.2 - Powers of Attorney.
/s/ Claudia Hanover, Attorney-in-Fact for Keystone International Acquisition Management LLC 06/02/2026
** Signature of Reporting Person Date
/s/ Claudia Hanover, Attorney-in-Fact for Jae Hyun (James) Park 06/02/2026
** Signature of Reporting Person Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

ATTACHMENTS / EXHIBITS

POWER OF ATTORNEY

POWER OF ATTORNEY

JOINT FILER INFORMATION, WHICH IS INCORPORATED HEREIN BY REFERENCE AND DESCRIBES IN FURTHER DETAIL THE RELATIONSHIPS OF THE REPORTING PERSONS TO THE ISSUER


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