(Amendment) Notice Regarding Amendment to “Notice Regarding Commencement of Tender Offer for Shares of TOA Oil Co., Ltd. (Securities Code: 5008)” in Connection with Submission of Amended Statement of Tender Offer Registration Statement（PDF：396KB）

January 29, 2021

Press Release

Company Name: Idemitsu Kosan Co.,Ltd. Representative Director & Chief Executive Officer: Shunichi Kito

(Company Code: 5019, TSE, First Sect.) Contact person:

Munehiro Sekine, General Manager,

Investor Relations Office, Finance Department (TEL: [phone])

(Amendment) Notice Regarding Amendment to "Notice Regarding Commencement of Tender Offer for Shares of TOA Oil Co., Ltd. (Securities Code: 5008)" in Connection with Submission of Amended Statement of Tender Offer Registration Statement

With regard to the tender offer (the "Tender Offer") for the shares of common stock of TOA Oil Co., Ltd. (the "Target Company") under the Financial Instruments and Exchange Act of Japan (Act No. 25 of 1948, as amended; the "Act"), it became necessary for Idemitsu Kosan Co., Ltd. (the "Tender Offeror") to amend certain matters contained in the tender offer registration statement that it submitted to the Director-General of the Kanto Local Finance Bureau on December 16, 2020 (including amended matters in the amended statement of the tender offer registration statement that it submitted to the Director-General of the Kanto Local Finance Bureau on December 21, 2020) in connection with the Target Company's announcement titled "Announcement Concerning Revision of Forecasts of Consolidated Results for Fiscal Year Ending March 2021" dated January 29, 2021. In order to amend these matters, the Tender Offeror submitted an amended statement of the tender offer registration statement to the Director-General of the Kanto Local Finance Bureau pursuant to Article 27- 8(2) of the Act on January 29, 2021.

In connection with this, the Tender Offeror hereby announces that the contents of the "Notice Regarding Commencement of Tender Offer for Shares of TOA Oil Co., Ltd. (Securities Code: 5008)" dated December 15, 2020 are amended as indicated below.

The amended language is underlined below.

1. Purpose of the Purchase

1. Overview of the Tender Offer
   (Before the Amendment)

For details regarding the Target Company's board of directors resolutions stated above, please refer to the Target Company Press Release, as well as "(vi) Approval of All Directors (Including Those Who are Audit and Supervisory

1

Committee Members) of the Target Company Without Conflicts of Interest" of "(Measures to Ensure Fairness of the Tender Offer, Such as Measures to Ensure Fairness of the Tender Offer Price as Well as Measures to Avoid Conflicts of Interest)" of "(II) Details of the Valuation" of "(4) Basis for Valuation of the Purchase Price" of "2. Overview of the Purchase" below.

(After the Amendment)

For details regarding the Target Company's board of directors resolutions stated above, please refer to the Target Company Press Release, as well as "(vi) Approval of All Directors (Including Those Who are Audit and Supervisory Committee Members) of the Target Company Without Conflicts of Interest" of "(Measures to Ensure Fairness of the Tender Offer, Such as Measures to Ensure Fairness of the Tender Offer Price as Well as Measures to Avoid Conflicts of Interest)" of "(II) Details of the Valuation" of "(4) Basis for Valuation of the Purchase Price" of "2. Overview of the Purchase" below.

Thereafter, the Target Company issued the "Announcement Concerning Revision of Forecasts of Consolidated Results for Fiscal Year Ending March 2021" on January 29, 2021, and the forecasts of the consolidated results for the fiscal year ending March 2021 (from April 1, 2020 to March 31, 2021) announced by the Target Company on July 31, 2020 were revised. As a result, changes occurred to the material facts that should be stated in the tender offer registration statement, and therefore, the Tender Offeror submitted an amended statement of the tender offer registration statement to the Director- General of the Kanto Local Finance Bureau pursuant to Article 27-8(2) of the Act. In connection with the submission of the amended statement, pursuant to Article 27-8(8) of the Act, the Tender Offeror extended the purchase period of the Tender Offer to February 15, 2021, which is the day on which ten business days will have elapsed from January 29, 2021, the submission date of the amended statement.

1. Post-TenderOffer Reorganization Policy (Matters Regarding a So-called"Two-Step Acquisition")

1. Share Consolidation

(Before the Amendment)

On the other hand, if, following the completion of the Tender Offer, the total number of the Target Company's voting rights owned by the Tender Offeror is less than 90% of all of the voting rights for the Target Company, the Tender Offeror will, promptly after completion of the settlement of the Tender Offer, request the Target Company to hold a special shareholders' meeting (the "Special Shareholders' Meeting") and for proposals to be submitted which will include (i) implementation of consolidation of Target Company Shares in accordance with Article 180 of the Companies Act (the "Share Consolidation"), and (ii) subject to the Share Consolidation being effective, changes to the Target Company's articles of incorporation that will eliminate provisions on a share unit number. The Tender Offeror considers that it is desirable for the Target Company to hold the Special Shareholders' Meeting as soon as possible from the perspective of improving the Target Company's corporate value. Therefore, the Tender Offeror plans to ask the Target Company to make a public notice during the purchase period of the Tender Offer (the "Tender Offer Period") setting the record date for the Special Shareholders' Meeting so that such record date will be a date shortly after the start date of the settlement of the Tender Offer (as of today, such date is planned to be February 10, 2021) and to target to hold the Special Shareholders' Meeting in late March or early Aprilof the same year. The Tender Offeror will approve each of the proposals above at the Special Shareholders' Meeting.

(After the Amendment)

On the other hand, if, following the completion of the Tender Offer, the total number of the Target Company's voting rights owned by the Tender Offeror is less than 90% of all of the voting rights for the Target Company, the Tender

2

Offeror will, promptly after completion of the settlement of the Tender Offer, request the Target Company to hold a special shareholders' meeting (the "Special Shareholders' Meeting") and for proposals to be submitted which will include (i) implementation of consolidation of Target Company Shares in accordance with Article 180 of the Companies Act (the "Share Consolidation"), and (ii) subject to the Share Consolidation being effective, changes to the Target Company's articles of incorporation that will eliminate provisions on a share unit number. The Tender Offeror considers that it is desirable for the Target Company to hold the Special Shareholders' Meeting as soon as possible from the perspective of improving the Target Company's corporate value. Therefore, the Tender Offeror plans to ask the Target Company to make a public notice during the purchase period of the Tender Offer (the "Tender Offer Period") setting the record date for the Special Shareholders' Meeting so that such record date will be a date shortly after the start date of the settlement of the Tender Offer (as of today, such date is planned to be February 23, 2021) and to target to hold the Special Shareholders' Meeting in early or late Aprilof the same year. The Tender Offeror will approve each of the proposals above at the Special Shareholders' Meeting.

2. Overview of the Purchase

1. Schedule, Etc.

1. Purchase Period Originally Specified in the Registration Statement
   (Before the Amendment)
   From December 16, 2020 (Wednesday) until February 2, 2021 (Tuesday) (30business days)

(After the Amendment)

From December 16, 2020 (Wednesday) until February 15, 2021 (Monday) (38business days)

1. Basis for Valuation of the Purchase Price

1. Details of the Valuation

1. Measures to Secure Purchase Opportunities from Other Buyers

(Before the Amendment)

The Tender Offeror has not entered into any agreement with the Target Company that limits the opportunities for the Target Company to have contact with a competing offeror, such as an agreement that includes deal protection provisions which prohibit the Target Company from having contact with a competing offeror.

Furthermore, the Tender Offeror has set a Tender Offer Period of 30 business days, which is longer than the minimum period of 20 business days provided by relevant laws and regulations. By setting such a comparatively long Tender Offer Period, the Tender Offeror intends to secure an appropriate opportunity to allow the Target Company shareholders to decide whether to tender their shares in the Tender Offer, and at the same time, to ensure opportunities for a potential purchaser other than the Tender Offeror to make a competing offer and to ensure the appropriateness of the Tender Offer Price.

(After the Amendment)

The Tender Offeror has not entered into any agreement with the Target Company that limits the opportunities for the Target Company to have contact with a competing offeror, such as an agreement that includes deal protection provisions which prohibit the Target Company from having contact with a competing offeror.

Furthermore, the Tender Offeror has set a Tender Offer Period of 30 business days, which is longer than the

3

minimum period of 20 business days provided by relevant laws and regulations. Thereafter, the Target Company issued the "Announcement Concerning Revision of Forecasts of Consolidated Results for Fiscal Year Ending March 2021" on January 29, 2021, and the forecasts of the consolidated results for the fiscal year ending March 2021 (from April 1, 2020 to March 31, 2021) announced by the Target Company on July 31, 2020 were revised. As a result, changes occurred to the material facts that should be stated in the tender offer registration statement, and therefore, the Tender Offeror submitted an amended statement of the tender offer registration statement to the Director-Generalof the Kanto Local Finance Bureau pursuant to Article 27-8(2)of the Act. In connection with the submission of the amended statement, pursuant to Article 27-8(8)of the Act, the Tender Offeror extended the purchase period of the Tender Offer to February 15, 2021, which is the day on which ten business days will have elapsed from January 29, 2021, the submission date of the amended statement. As a result, the Tender Offer Period became 38 business days.By setting such a comparatively long Tender Offer Period, the Tender Offeror intends to secure an appropriate opportunity to allow the Target Company shareholders to decide whether to tender their shares in the Tender Offer, and at the same time, to ensure opportunities for a potential purchaser other than the Tender Offeror to make a competing offer and to ensure the appropriateness of the Tender Offer Price.

1. Settlement Method

1. Commencement Date of Settlement
   (Before the Amendment) February 9, 2021 (Tuesday)

(After the Amendment)

February 22, 2021 (Monday)

4. Other Information

1. Other Information Deemed Necessary for the Investors in Deciding Whether to Apply for the Tender Offer

(Before the Amendment)

1. Non-paymentof Dividends by the Target Company for Fiscal Year Ending 2021

At the board of directors meeting of the Target Company held today, the Target Company resolved not to pay year-end dividends for the fiscal year ending 2021, revising its dividend forecast for the fiscal year ending 2021, subject to the successful completion of the Tender Offer. For the details, please refer to the "Announcement Concerning Revision of Dividend Forecast for Fiscal Year Ending 2021 (Non-payment of Dividends)" published today by the Target Company.

(After the Amendment)

1. Non-paymentof Dividends by the Target Company for Fiscal Year Ending 2021
   At the board of directors meeting of the Target Company held today, the Target Company resolved not to pay

year-end dividends for the fiscal year ending 2021, revising its dividend forecast for the fiscal year ending 2021, subject to the successful completion of the Tender Offer. For the details, please refer to the "Announcement Concerning Revision of Dividend Forecast for Fiscal Year Ending 2021 (Non-payment of Dividends)" published today by the Target Company.

1. Issuance of the "Announcement Concerning Revision of Forecasts of Consolidated Results for Fiscal Year Ending
   4