Major Shareholder Report: Share Pledge Contract Amendment — Dongjin Semichem

Summary

Dongjin Holdings, the largest shareholder, filed an amended major shareholding report reflecting a change in its share pledge contract. The shares pledged under key contracts decreased from 1,096,651 (2.13%) to 878,159 (1.72%), while the total holding of 17,757,724 shares remained unchanged. The ownership ratio rose slightly from 34.54% to 34.84% due to a reduction in total voting shares from treasury stock cancellation. The number of special-related parties decreased from 4 to 3. No actual share transactions occurred; the filing reflects only a pledge contract modification.

Historical Impact

9 past Large Holding Report (5%+) · ≈ Schedule 13D/G events at Dongjin Semichem

Median +5d

-0.57%

Range

-8.21% to +19.63%

Positive outcomes

4/9

Filed	P₀	P₊₅	+5d
May 29, 2026	₩54,700	₩50,600	-7.50%
May 4, 2026	₩58,900	₩56,200	-4.58%

Full Translation

Report on Mass Holding of Stocks (General) Dongjin Semichem Co., Ltd. Report on Mass Holding of Stocks (General Form: filings under Article 147 of the Financial Investment Services and Capital Markets Act, for the purpose of 'influencing management control') To: Financial Services Commission Reporting Obligation Date: June 1, 2026 To: Korea Exchange Report Preparation Date: June 8, 2026 Reporter: Dongjin Holdings [Summary Information] Issuing Company: Dongjin Semichem Co., Ltd. Relationship to Issuer: Largest Shareholder Report Type: Amendment Number and Ratio of Shares Held: - Previous Report: 17,757,724 shares (34.54%) - Current Report: 17,757,724 shares (34.84%) Number and Ratio of Shares under Major Contracts: - Previous Report: 1,096,651 shares (2.13%) - Current Report: 878,159 shares (1.72%) Voting Rights and Ratio: None reported Reason for Report: Amendment of share pledge contract Part 1: Overview of Report 1. Issuing Company - Company Name: Dongjin Semichem Co., Ltd. - Company Code: 005290 - Classification: KOSDAQ-listed corporation - Total Voting Shares Issued: 50,970,126 2. Large Shareholder A. Reporter - Report Type: Amendment - Joint Filing: Yes - Classification: Domestic corporation - Nationality: Republic of Korea - Name: Dongjin Holdings (DONGJIN HOLDINGS CO., LTD) - Address: Baekbeom-ro, Seo-gu, Incheon - Business Registration No.: 137-81-09961 - Business: Holding company business - Relationship to Issuer: Largest shareholder - Contact: Sim Chi-heon, Finance Team Manager, Dongjin Semichem (Tel: 02-635-****) Reporter Details (as of December 31, 2025 audit report): - Legal form: Stock corporation - Total assets: KRW 102,702,420,703 - Total liabilities: KRW 20,992,069,912 - Total equity: KRW 81,710,350,791 - Capital stock: KRW 15,529,285,000 - Representative: Lee Jun-hyuk - Decision-making body: Board of Directors - Largest shareholder: Lee Jun-hyuk (35.72%) B. Special-Related Parties: 1. Myeongbu Industries — domestic corporation, real estate business, shareholder (Business No. 105-81-02904) 2. Ok Yeon-su — domestic individual, shareholder 3. An Sang-hee — overseas individual (USA), shareholder Myeongbu Industries Details: - Legal form: Stock corporation - Total assets: KRW 7,036,858,877 - Total liabilities: KRW 5,850,799,297 - Total equity: KRW 1,186,059,580 - Capital stock: KRW 50,000,000 - Representative: Lee Jun-hyuk - Largest shareholder: Lee Jun-hyuk (90.00%) 3. Number and Ratio of Shares Held - Previous Report (2026.01.30): Dongjin Holdings + 4 related parties, 17,757,724 shares (34.54%), total voting shares 51,414,494 - Current Report (2026.06.08): Dongjin Holdings + 3 related parties, 17,757,724 shares (34.84%), total voting shares 50,970,126 - Change: 0 shares (+0.30%p), total voting shares -444,368 - Note: The decrease in total voting shares is due to cancellation of the issuer's treasury stock. 4. Purpose of Holding: Influence over management control The reporter and special-related parties exercise influence as the largest shareholder over matters including: (1) appointment/dismissal of directors and auditors, (2) changes to articles of incorporation regarding corporate organs, (3) changes in capital, (4) mergers/spin-offs, (5) comprehensive share exchanges/transfers, (6) transfer of business, (7) disposal of assets, (8) leasing of business or management delegation, (9) corporate dissolution. No specific plans currently exist regarding these matters. 5. Reason for Change/Amendment - Change method: Not applicable - Change reason: Not applicable - Amendment reason: Amendment of share pledge contract Part 2: Mass Holding Details 1. Holdings by Reporter and Special-Related Parties A. Holdings by Type of Securities (Common Stock): - Dongjin Holdings: 16,706,986 shares (32.78%) - Myeongbu Industries: 633,678 shares (1.24%) - Ok Yeon-su: 210,560 shares (0.41%) - An Sang-hee: 206,500 shares (0.41%) - Total Voting Shares Issued: 50,970,126 - Total Holding Ratio: 34.84% B. Holdings by Form (Article 142 of Enforcement Decree): - Dongjin Holdings: 16,706,986 shares (32.78%) — Type 1 - Myeongbu Industries: 633,678 shares (1.24%) — Type 1 - Ok Yeon-su: 210,560 shares (0.41%) — Type 1 - An Sang-hee: 206,500 shares (Type 1) [Translation truncated]