[Amended] Change of largest shareholder

What happened

Company: Duoback / Change of Largest Shareholder / (2026.09.18) Correction Report on Change of Largest Shareholder

Correction Date: 2026-09-18

1. Public Disclosure Document Subject to Correction: Change of Largest Shareholder

2. Submission Date of Public Disclosure Document Subject to Correction: 2026-09-18

3. Reason for Correction: Correction disclosure due to name transfer of heir

4. Correction Details

Correction Item | Before Correction | After Correction 1. Change Details - After Change | Largest Shareholder etc.: Jung Young-ah and 5 others | Owned Shares (shares): 5,278,486 | Ownership Ratio (%): 44.10 3. Purpose of Equity Acquisition - | Succession of equity due to inheritance 4. Date of Change - | 2026-08-17 5. Date of Change Confirmation - | 2026-09-18 6. Other Matters for Investment Decision Reference - | Further correction disclosure is planned after inheritance is finalized. This correction disclosure is with respect to the "Change of Largest Shareholder" disclosed on August 19, 2026, and the matters regarding the largest shareholder after the change have been confirmed upon completion of name transfer. The change of largest shareholder is due to inheritance following the death of the existing largest shareholder. Pursuant to the agreement on division of inherited property, all 4,351,102 shares held by the deceased were solely inherited by the spouse. There is no change in the number of shares owned and ownership ratio of the largest shareholder etc. The ownership ratio (%) stated in "1. Change Details" above and in "Detailed Change Details" below is calculated based on total issued shares of 11,968,040. The "4. Date of Change" above is the date of commencement of inheritance, and "5. Date of Change Confirmation" is the completion date of name transfer due to inheritance. The matters regarding the largest shareholder after the change are confirmed upon completion of name transfer of inherited shares.

Change of Largest Shareholder

1. Change Details

Before Change | Largest Shareholder etc.: Jung Kwan-young and 5 others | Owned Shares (shares): 5,278,486 | Ownership Ratio (%): 44.10 After Change | Largest Shareholder etc.: Jung Young-ah and 5 others | Owned Shares (shares): 5,278,486 | Ownership Ratio (%): 44.10

2. Reason for Change: Commencement of inheritance due to death of largest shareholder - Whether change due to acquisition of forfeited shares: No - Whether mandatory holding of acquired shares: No

3. Purpose of Equity Acquisition: Succession of equity due to inheritance - Method of raising acquisition funds: Own funds (KRW) - Borrowed funds (KRW) - Lender - Borrowing period - ~ - Collateral details - - Plan for appointment/dismissal of officers after acquisition -

4. Date of Change: 2026-08-17

5. Date of Change Confirmation: 2026-09-18

6. Other Matters for Investment Decision Reference - This correction disclosure is with respect to the "Change of Largest Shareholder" disclosed on August 19, 2026, and the matters regarding the largest shareholder after the change have been confirmed upon completion of name transfer. - The change of largest shareholder is due to inheritance following the death of the existing largest shareholder. Pursuant to the agreement on division of inherited property, all 4,351,102 shares held by the deceased were solely inherited by the spouse. There is no change in the number of shares owned and ownership ratio of the largest shareholder etc. - The ownership ratio (%) stated in "1. Change Details" above and in "Detailed Change Details" below is calculated based on total issued shares of 11,968,040. - The "4. Date of Change" above is the date of commencement of inheritance, and "5. Date of Change Confirmation" is the completion date of name transfer due to inheritance.

Related Disclosure: 2026-08-19 Change of Largest Shareholder

[Detailed Change Details]

Name (Corporate Name, Partnership Name, Other Organization Name) | Relationship | Before Change (Shares/Ownership Ratio %) | After Change (Shares/Ownership Ratio %) | Remarks

Jung Kwan-young | Former Largest Shareholder | 4,351,102 shares / 36.36% | - / - | Inheritance due to death Jung Young-ah | Latter Largest Shareholder | - / - | 4,351,102 shares / 36.36% | Spouse of deceased Oh Jun-sung | Related Party of Former Largest Shareholder | 125,704 shares / 1.06% | 125,704 shares / 1.06% | Related Party (Relative) of Latter Largest Shareholder Jung Woo-seok | Related Party of Former Largest Shareholder | 200,400 shares / 1.67% | 200,400 shares / 1.67% | Related Party (Child) of Latter Largest Shareholder Jung Woo-jin | Related Party of Former Largest Shareholder | 200,400 shares / 1.67% | 200,400 shares / 1.67% | Related Party (Child) of Latter Largest Shareholder Jung Woo-chan | Related Party of Former Largest Shareholder | 200,440 shares / 1.67% | 200,440 shares / 1.67% | Related Party (Child) of Latter Largest Shareholder Jung Woo-hyun | Related Party of Former Largest Shareholder | 200,440 shares / 1.67% | 200,440 shares / 1.67% | Related Party (Child) of Latter Largest Shareholder

[Matters Regarding the Latter Largest Shareholder (Individual)]

1. Basic Information of Individual Name: Jung Young-ah Nationality: Republic of Korea

Executive Career of Individual: Not applicable

History as Largest Shareholder of Listed Company: Not applicable

2. Relationship between the Listed Company and the Largest Shareholder (Individual): Not applicable

3. Transaction Details between the Listed Company and the Largest Shareholder (Individual) in the Last Three Years (excluding routine transactions) Current Year: - Previous Year: - Year Before Previous: -