Material event report (decision to redeem own convertible bonds early)

What happened

Material Report (Decision on Early Acquisition of Own Convertible Bonds) 6.0 OncocrosS Co., Ltd. Material Report / Exchange Reporting Obligation Financial Services Commission / Korea Exchange September 18, 2026 Company Name: OncocrosS Co., Ltd. Representative Director: Kim Yi-rang / Kang Ji-hoon (each as co-representative director) Head Office Address: Room 905, 7 Beophwon-ro 11-gil, Songpa-gu, Seoul (Munjeong-dong, Munjeong Hyundai Knowledge Industry Center 1-2) (Telephone) 02-867-9967 (Website) http://www.oncocross.com Preparer: (Position) Senior Managing Director (Name) Chae Hee-jin (Telephone) 02-867-9967

Decision on Early Acquisition of Own Convertible Bonds

1. Type of Bond: Series 1, Type: Bearer-form Interest-bearing Unsecured Private Placement Convertible Bond

2. Bond Issuance Date: July 25, 2025

3. Bond Issuance Method: Private Placement

4. Bond Maturity Date: July 25, 2030

5. Total Face Value (Electronic Registration) of Bond (KRW): 12,500,000,000

6. Face Value (Electronic Registration) of Bond Subject to Acquisition (KRW): 2,500,000,000

7. Acquisition Decision Date: September 18, 2026

8. Acquisition Amount: KRW 2,559,286,113. Calculation Basis: Principal and interest payment (scheduled) date September 30, 2026. Source of acquisition funds: Own funds.

9. Acquisition Method: Over-the-counter purchase

10. Reason for Early Acquisition: Exercise of issuer's call option

11. Future Handling Plan: The specific handling direction of the acquired own convertible bonds will be determined separately at a later date.

12. Conversion Matters: Conversion ratio (%) 100. Conversion price as of reporting date (KRW/share) 8,493. Type of shares to be issued upon conversion: OncocrosS Co., Ltd. registered ordinary shares. Number of shares: 294,360. Ratio to total shares (%) 2.21. Conversion request period: Start date July 25, 2026, End date June 25, 2030.

13. Remaining Face Value (Electronic Registration) of Bond After Acquisition (KRW): 10,000,000,000

14. Fair Trade Commission Reporting Requirement: Not applicable

15. Other Matters for Reference in Investment Decisions:

1) This acquisition of own convertible bonds is conducted through the exercise of a call option pursuant to a separate agreement entered into with the bondholder regarding the Series 1 Bearer-form Interest-bearing Unsecured Private Placement Convertible Bond issued by the Company on July 25, 2025.

2) Pursuant to the separate agreement, the Company exercises the call option with respect to KRW 2,500,000,000, which represents 20% of the total bond issuance amount.

3) The "Acquisition Decision Date" stated in item 7 above is the date of board resolution regarding the exercise of the call option and acquisition of the own convertible bonds.

4) The "Acquisition Amount" stated in item 8 above is calculated by applying an annual interest rate of 2.0% (compounded quarterly) from the bond issuance date to the day before the transaction date to the electronic registration amount of the bond subject to acquisition, as determined in the separate agreement, with amounts less than one won truncated. The payment (scheduled) date of the "Acquisition Amount" is the date on which the acquisition of the bond is expected to be completed.

5) Regarding the "Future Handling Plan" stated in item 11 above, no specific handling direction for the acquired own convertible bonds has been determined at present, and such direction will be determined separately at a later date.

【Information Regarding Sellers】

Seller Name: Korea Investment & Securities Co., Ltd. (in capacity as trustee of Fund 1 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 260,000,000. Remarks: -

Seller Name: Korea Investment & Securities Co., Ltd. (in capacity as trustee of Fund 2 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 700,000,000. Remarks: -

Seller Name: Korea Investment & Securities Co., Ltd. (in capacity as trustee of Fund 3 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 240,000,000. Remarks: -

Seller Name: Korea Investment & Securities Co., Ltd. (in capacity as trustee of Fund 4 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 100,000,000. Remarks: -

Seller Name: NH Investment & Securities Co., Ltd. (in capacity as trustee of Fund 5 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 100,000,000. Remarks: -

Seller Name: Korea Investment & Securities Co., Ltd. (in capacity as trustee of Fund 6 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 100,000,000. Remarks: -

Seller Name: Korea Investment & Securities Co., Ltd. (in capacity as trustee of Fund 7 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 100,000,000. Remarks: -

Seller Name: KB Securities Co., Ltd. (in capacity as trustee of Fund 8 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 200,000,000. Remarks: -

Seller Name: NH Investment & Securities Co., Ltd. (in capacity as trustee of Fund 9 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 200,000,000. Remarks: -

Seller Name: Mirae Asset Securities Co., Ltd. (in capacity as trustee of Fund 10 in this matter) - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 200,000,000. Remarks: -

Seller Name: KR&Partners Co., Ltd. - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 200,000,000. Remarks: -

Seller Name: Painters&Ventures Co., Ltd. - Relationship with company or largest shareholder: - Selection process: Sale pursuant to exercise of call option. Transactions and plans within 6 months before and after acquisition decision: No applicable matters. Face value of bonds sold (KRW): 100,000,000. Remarks: -

【Information Regarding Corporations or Organizations Among Sellers】

(1) Basic Information on Corporations or Organizations

Name: Painters&Ventures Co., Ltd. Number of investors (persons): 7. Representative Director: Lee Jung-hoon (16.66% stake). Executive officer: Lee Jung-hoon (16.66% stake). Largest shareholder (largest investor): C&K P Co., Ltd. (40.00% stake).

(2) Key Financial Information of Corporation or Organization at Most Recent Fiscal Year-End (Unit: Million KRW)

Fiscal Year: 2025. Fiscal Year-End: December. Total Assets: 3,470. Sales: 1,038. Total Liabilities: 508. Net Income (Loss) for the Period: -60. Total Capital: 2,961. External Auditor: Donghang Accounting Firm. Capital: 2,794. Audit Opinion: Appropriate.