Large Shareholding Change: Controlling Shareholder & Related Parties Buy Shares for Price Stabilization

LARGE SHAREHOLDING REPORT (GENERAL) Version: 6.0 Company: Cheonbo Co., Ltd. Large Shareholding Report (General Form: Report under Article 147 of the Financial Investment Services and Capital Markets Act — for the purpose of 'influencing management control') To: Financial Services Commission To: Korea Exchange Date obligation to report arose: June 26, 2026 Report preparation base date: June 26, 2026 Reporter: Lee Sang-ryul --- SUMMARY INFORMATION --- Issuing Company: Cheonbo Co., Ltd. Relationship with Issuing Company: Largest Shareholder Report Type: Change Shares Held (number / ratio): Previous report: 8,101,206 shares / 55.31% This report: 8,146,039 shares / 55.62% Shares Subject to Major Contracts (number / ratio): Previous report: — / — This report: — / — Voting Rights Held (number / ratio): Previous report: 5,705,595 votes / 46.56% This report: 5,750,428 votes / 46.93% Voting Rights Subject to Major Contracts: Previous report: — / — This report: — / — Reason for Report: - Controlling shareholder share purchase - Related party share purchase ※ The reporter confirms that as of the report preparation base date, the shareholding status of the reporter and specially related parties has been accurately recorded in accordance with applicable laws and disclosure guidelines, and that there are no material misstatements or omissions. === PART 1: OVERVIEW OF THE REPORT === 1. Information about the Issuing Company Company Name: Cheonbo Co., Ltd. Company Code: 278280 Corporate Classification: KOSDAQ-listed corporation Total voting shares issued: 12,253,025 2. Information about the Large Shareholder A. Reporter (1) Reporter Overview Report Type: Change Joint Report: No Reporter Classification: Individual (domestic) Nationality: Republic of Korea Name (Korean): 이상율 Name (Chinese/English): 李相律 / LEE SANG RYUL Address (up to town/village/neighborhood): Jungangtan-myeon, Chungju-si, Chungcheongbuk-do Date of Birth: October 21, 1961 (611021) Occupation: CEO of Cheonbo Co., Ltd. Relationship with Issuing Company: Largest Shareholder Contact for Business Purposes: Affiliated Company: Cheonbo Co., Ltd. Department: Management Team Title: Deputy General Manager (Chajang) Phone: 070-48******* Name: Yun Hong-hwan Fax: 043-84****** Email: ******1@chunbochem.com (2) Specific Details about the Reporter (applicable to corporations, organizations, statutory partnerships, civil law partnerships): Legal Nature: — Total Assets (or AUM): — Total Liabilities: — Total Equity: — Paid-in Capital: — Representative: — Decision-making Body: — Largest Shareholder: — Largest Shareholder Ownership (%): — B. Specially Related Parties (1) Overview of Specially Related Parties No. | Name | Classification | Specific Relationship with Reporter | DOB / Business Reg. No. | Nationality | Address | Relationship with Issuing Company 1 | Seo Ja-won | Individual (dom.)| CEO | 620809 | Korea | Jungangtan-myeon, Chungju-si, Chungcheongbuk-do | Major Shareholder 2 | Lee Seul-ji | Individual (dom.)| Family/Relative | 940702 | Korea | Samseong-ro, Gangnam-gu, Seoul | Shareholder 3 | Lee Hyeon-ji | Individual (dom.)| Family/Relative | 951207 | Korea | Jungangtan-myeon, Chungju-si, Chungcheongbuk-do | Shareholder 4 | Lee Yeong-seok | Individual (dom.)| Family/Relative | 860714 | Korea | Jungangtan-myeon, Chungju-si, Chungcheongbuk-do | Shareholder 5 | Choe Byeong-min | Individual (dom.)| Family/Relative | 681101 | Korea | Cheoncheon-ro, Jangan-gu, Suwon-si, Gyeonggi-do | Shareholder 6 | Sin Su-il | Individual (dom.)| Family/Relative | 710922 | Korea | Suin-ro, Siheung-si, Gyeonggi-do | Shareholder 7 | Lee Sang-eun | Individual (dom.)| Family/Relative | 510126 | Korea | Gyohyeon-dong, Chungju-si, Chungcheongbuk-do | Shareholder 8 | Ju Hye-sin | Individual (dom.)| Family/Relative | 940511 | Korea | Pyeongchon-daero, Dongan-gu, Anyang-si, Gyeonggi-do | Shareholder 9 | Ju Hye-yeon | Individual (dom.)| Family/Relative | 960828 | Korea | Pyeongchon-daero, Dongan-gu, Anyang-si, Gyeonggi-do | Shareholder 10 | Lee Un-jong | Individual (dom.)| Family/Relative | 740113 | Korea | Dongtan-daero, Hwaseong-si, Gyeonggi-do | Shareholder 11 | Cheonbo Precision | Domestic Corp. | Affiliate | 504-81-25026 | Korea | Samseong-myeon, Eumseong-gun, Chungcheongbuk-do | Affiliate 12 | Solique Investment | Domestic Corp. | Affiliate | 394-88-01902 | Korea | Yeongdong-daero, Gangnam-gu, Seoul | Affiliate 13 | U Dong-hui | Individual (dom.)| Officer | 620830 | Korea | Sinmok-ro, Yangcheon-gu, Seoul | Registered Officer 14 | Lee Geun-pil | Individual (dom.)| Officer | 701218 | Korea | Wicity 1-ro, Ilsandong-gu, Goyang-si, Gyeonggi-do | Registered Officer * Addresses listed only to town/village/neighborhood level. (2) Specific Details about Specially Related Parties (corporations/organizations) Cheonbo Precision Co., Ltd. (Unit: KRW millions) Legal Nature: Corporation (Jusik Hoesa) Total Assets: 35,446 Total Liabilities: 9,305 Total Equity: 26,141 Paid-in Capital: 200 Representative: Lee Sang-ryul Decision-making Body: General Shareholders' Meeting, Board of Directors Largest Shareholder: Lee Sang-ryul Largest Shareholder Ownership: 47.5% Solique Investment Co., Ltd. (Unit: KRW millions) Legal Nature: Corporation (Jusik Hoesa) Total Assets: 22,394 Total Liabilities: 32 Total Equity: 22,362 Paid-in Capital: 20,000 Representative: Ryu Si-myeong Decision-making Body: General Shareholders' Meeting, Board of Directors Largest Shareholder: Cheonbo Precision Co., Ltd. Largest Shareholder Ownership: 50.9% C. Collective Investment Manager: N/A (not applicable) 3. Number and Ratio of Shares Held Base Date | Reporter | # Special Related | Total Shares | Ratio (%) | Voting Shares | Voting Ratio (%) | Total Voting Shares Issued Previous Report | Lee Sang-ryul | 14 | 8,101,206 | 55.31 | 5,705,595 | 46.56 | 12,253,025 (June 25, 2026) This Report | Lee Sang-ryul | 14 | 8,146,039 | 55.62 | 5,750,428 | 46.93 | 12,253,025 (June 26, 2026) Change | | | +44,833 | +0.31 | +44,833 | +0.37 | 0 4. Purpose of Holding Purpose: Influence over Management Control The reporter exercises de facto influence over the following matters: 1. Appointment/dismissal of directors and auditors, or suspension of their duties 2. Amendments to the articles of incorporation related to the board of directors and other corporate organs 3. Changes to the company's paid-in capital 4. Decisions on the company's dividends 5. Merger, division, and split-merger of the company 6. Comprehensive share exchange and transfer 7. Transfer or acquisition of all or a materially significant portion of the business as designated by the FSC 8. Disposal of all assets or a materially significant portion thereof as designated by the FSC 9. Lease of the entire business, entrustment of management, contracts to share all profit and loss with another party, and the conclusion, modification, or termination of similar contracts 10. Dissolution of the company The reporter exercises de facto influence over all of the above matters and intends to make decisions related to corporate management activities in a manner consistent with the company's business objectives. 5. Reason for Change Method of Change: - Controlling shareholder share purchase - Related party share purchase Reason for Change: - Stock price stabilization and enhancement of shareholder value Reason for Modification: — === PART 2: DETAILS OF LARGE HOLDINGS === 1. Holdings by Reporter and Specially Related Parties A. Holdings by Type of Securities Relationship | Name | DOB/Reg. No. | Common Stock (Voting) | Warrants | CBs | BWs | Exchangeable Bonds | DRs | Other | Total Shares | Total Ratio (%) Reporter | Lee Sang-ryul | 611021 | 3,416,000 | — | — | — | 958,244 | — | — | 4,374,244 | 29.86 Related | Seo Ja-won | 620809 | 1,037,065 | — | — | — | — | — | — | 1,037,065 | 7.08 Related | Lee Seul-ji | 940702 | 535,000 | — | — | — | 287,474 | — | — | 822,474 | 5.61 Related | Lee Hyeon-ji | 951207 | 515,000 | — | — | — | 958,244 | — | — | 1,473,244 | 10.06 Related | Lee Yeong-seok | 860714 | 12,580 | — | — | — | — | — | — | 12,580 | 0.09 Related | Choe Byeong-min | 681101 | [data truncated in source] [Translation truncated — source disclosure was cut off mid-table during the per-holder breakdown of Lee Yeong-seok and Choe Byeong-min's entries and all subsequent holders.]