Keystone Acquisition Corp. (KEYYU) director discloses 25,000 convertible Class B shares on Form 3

Q: How many Keystone Acquisition Corp. Class B shares does the director hold?

Director Cho Paul Yoonku holds 25,000 Class B ordinary shares . According to the disclosure, these Class B shares are convertible into 25,000 Class A ordinary shares , providing potential future common equity exposure if and when they are converted per the S-1 description.

Q: Are Keystone Acquisition Corp. Class B shares convertible into Class A shares?

Yes. The filing states the Class B ordinary shares are convertible into Keystone Acquisition Corp.’s Class A ordinary shares, as described under “Description of Securities” in the company’s Form S-1 Registration Statement, and the shares have no expiration date on that conversion right.

Q: What is the significance of the conversion terms disclosed for KEYUY’s Class B shares?

The Form 3 notes that Class B ordinary shares convert into Class A shares under terms in the Form S-1. This means the director’s 25,000 Class B shares can become 25,000 Class A shares, and the conversion feature has no expiration date according to the footnote.

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

Rhea-AI Filing Summary

Keystone Acquisition Corp. director Cho Paul Yoonku reported his initial beneficial ownership on a Form 3. He holds 25,000 Class B ordinary shares, which are convertible into 25,000 Class A ordinary shares as described in the company’s Registration Statement on Form S-1.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Cho Paul Yoonku

Role null

Type	Security	Shares	Price	Value
holding	Class B Ordinary Shares	--	--	--

Holdings After Transaction: Class B Ordinary Shares — 25,000 shares (Direct, null)

Footnotes (1)

[object Object]

Key Figures

Class B shares held: 25,000 shares Underlying Class A shares: 25,000 shares Exercise price: $0.0000 per share

3 metrics

Class B shares held 25,000 shares Total Class B ordinary shares directly owned following report

Underlying Class A shares 25,000 shares Class A ordinary shares underlying the Class B shares

Exercise price $0.0000 per share Conversion or exercise price stated for Class B into Class A

Key Terms

Class B Ordinary Shares, Class A Ordinary Shares, Registration Statement on Form S-1, convertible

4 terms

Class B Ordinary Shares financial

"The Class B ordinary shares are convertible for the Issuer's Class A ordinary shares"

Class B ordinary shares are a type of ownership stake in a company that typically come with different voting rights or privileges compared to other share classes. For investors, they represent a way to hold part of the company’s value and influence its decisions, often with fewer voting rights than Class A shares. Understanding these shares helps investors assess their level of control and potential returns within a company.

Class A Ordinary Shares financial

"Class B ordinary shares are convertible for the Issuer's Class A ordinary shares"

Class A ordinary shares are a type of ownership stake in a company that typically grants voting rights to shareholders, allowing them to have a say in important company decisions. They often come with priority in receiving dividends or profits, making them attractive to investors seeking influence and potential income. These shares help distinguish different levels of ownership and rights within a company's stock structure.

Registration Statement on Form S-1 regulatory

"as described under the heading "Description of Securities" in the Issuer's Registration Statement on Form S-1"

A registration statement on Form S-1 is a detailed filing a company submits to the U.S. securities regulator to register new shares for public sale; it includes a plain-language prospectus, financial statements, business description and risk factors. For investors it matters because it provides the official, comprehensive blueprint of the offering — like an owner’s manual — allowing buyers to assess risks, inspect financial health and compare valuation before deciding to invest.

convertible financial

"The Class B ordinary shares are convertible for the Issuer's Class A ordinary shares"

A convertible is a type of investment that starts as a loan or preferred stake (like a bond or preferred share) but can be exchanged for common shares of the company at a set price or under certain conditions. It matters to investors because it offers a mix of steady income and downside protection like a loan, plus the upside of stock ownership if the company does well—similar to holding a coupon that you can trade for a full ticket if the event becomes valuable.

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06/02/2026 - 09:54 PM

SEC Form 3

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

OMB APPROVAL

OMB Number:			3235-0104
Estimated average burden
hours per response:			0.5

1. Name and Address of Reporting Person^*

Cho Paul Yoonku

(Last)

(First)

(Middle)

C/O KEYSTONE ACQUISITION CORP.

142 WEST 57TH STREET, 11TH FLOOR

(Street)

NEW YORK

10019

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Date of Event Requiring Statement (Month/Day/Year)
06/02/2026

3. Issuer Name and Ticker or Trading Symbol
Keystone Acquisition Corp. [ KEYY ]

3a. Foreign Trading Symbol

5. If Amendment, Date of Original Filed (Month/Day/Year)

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	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)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	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)
Class B Ordinary Shares	⁽¹⁾	⁽¹⁾	Class A Ordinary Shares	25,000	⁽¹⁾	D

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.

Remarks:

See Exhibit 24.1 - Power of Attorney.

	/s/ Claudia Hanover, Attorney-in-Fact	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 5 (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.
* Form 3: SEC 1473 (03-26)

Source: View Original Filing on SEC EDGAR

FAQ

What does Keystone Acquisition Corp. (KEYYU) Form 3 report for Cho Paul Yoonku?

The Form 3 shows director Cho Paul Yoonku’s initial ownership of 25,000 Class B ordinary shares of Keystone Acquisition Corp. These Class B shares are convertible into an equal number of Class A ordinary shares under terms described in the company’s Form S-1 registration statement.

How many Keystone Acquisition Corp. Class B shares does the director hold?

Director Cho Paul Yoonku holds 25,000 Class B ordinary shares. According to the disclosure, these Class B shares are convertible into 25,000 Class A ordinary shares, providing potential future common equity exposure if and when they are converted per the S-1 description.

Are Keystone Acquisition Corp. Class B shares convertible into Class A shares?

Yes. The filing states the Class B ordinary shares are convertible into Keystone Acquisition Corp.’s Class A ordinary shares, as described under “Description of Securities” in the company’s Form S-1 Registration Statement, and the shares have no expiration date on that conversion right.

Does the Form 3 for KEYUY show any insider buy or sell transactions?

No explicit buy or sell transactions are reported. The Form 3 functions as an initial ownership report, listing 25,000 Class B ordinary shares held by director Cho Paul Yoonku, rather than documenting new purchases or sales in the market.

What is the significance of the conversion terms disclosed for KEYUY’s Class B shares?

The Form 3 notes that Class B ordinary shares convert into Class A shares under terms in the Form S-1. This means the director’s 25,000 Class B shares can become 25,000 Class A shares, and the conversion feature has no expiration date according to the footnote.