Mitsui Chemicals : 【Timely Disclosure】Notice Regarding the Status and Completion of Repurchase of Own Shares and the Number of Treasury Shares to be Cancelled

Company name: Mitsui Chemicals, Inc.

ICHIMURA Satoshi,

April 28, 2026

Name of representative:

Representative Director and President (Securities code: 4183 :Prime Market)

Inquiries:

TAKATAMA Yoshinori,

General Manager of Corporate Communications Division (Telephone: ＋81-3-6880-7500)

Mitsui Chemicals, Inc. (Tokyo: 4183; President & CEO: ICHIMURA Satoshi; "the Company") resolved, at the meeting of its Board of Directors held on February 5, 2026, to repurchase its own shares pursuant to Article 156 of the Companies Act as applied mutatis mutandis pursuant to Article 165, Paragraph 3 of the Act. The status of the share repurchase is as follows. With this, the repurchase of the Company's own shares has been completed, as the total repurchase amount has reached the upper limit. In addition, the Company hereby announces that the number of treasury shares to be cancelled pursuant to Article 178 of the Companies Act, as resolved at the same meeting of its Board of Directors, has been determined.

1. Status of repurchase of own shares

   1. Class of shares repurchased: Common shares of the Company

   2. Total number of shares repurchased: 6,584,000 shares

   3. Aggregate repurchased amount: 12,736,601,985 yen

   4. Period for repurchase: From April 1, 2026 to April 27, 2026

2. Details of cancellation of treasury shares

   1. Class of shares to be cancelled: Common shares of the Company

   2. Total number of shares to be cancelled: 20,100,256 shares

   3. Total number of issued shares after the cancellation: 381,587,374 shares

   4. Shcduled date of the cancellation: August 31, 2026

(Reference)

1. Details of resolution at the meeting of the Board of Directors held on February 5, 2026.

   1. Details of repurchase

      ①	Class of shares to be repurchased	Common shares of the Company
      ②	Total number of shares to be repurchased	Up to 18,400,000 shares (Percentage to the total number of shares in issue (excluding treasury shares) 4.9%)
      ③	Total amount of repurchase	Up to JPY 30,000,000,000
      ④	Repurchase period	From February 6, 2026 to July 31, 2026
      ⑤	Repurchase method	Market purchases based on a discretionary dealing contract regarding repurchase of its own shares

   2. Details of cancellation

      ①	Class of shares to be cancelled	Common shares of the Company
      ②	Number of shares to be cancelled	The number of treasury shares held by the Company will be reduced through cancellation so that, upon completion of the share repurchase pursuant to (1) above, it will be approximately 5% of the total number of shares in issue.
      ③	Scheduled date of cancellation	August 31, 2026

2. Total number of shares repurchased based on the above resolution of the Board of Directors (as of April 27, 2026)

   1. Number of shares repurchased: 15,000,400 shares

   2. Aggregate repurchased amount: 29,999,877,785 yen

3. Satus of shares in issue and treasury shares as of April 27, 2026

   1. The total number of shares in issue (excluding treasury shares): 361,502,993 shares

   2. Number of treasury shares

(including the total number of shares repurchased as stated in 2.(1) above): 40,184,637 shares