Investor Presentaiton

Petroleum Segment Business Overview as of the end of March 2023 [KB/D] Operating Refinery Company Refining Capacity RH FCC RFCC FLG Equity Ratio Japan Hokkaido 150 42 33 Idemitsu Kosan Chiba 190 40 45 Aichi 160 60 60 Showa Yokkaichi Yokkaichi 255 45 Sekiyu Toa Oil Keihin 70 42 50 50 61 75.0% 27 100.0% Seibu Oil Yamaguchi 120 52 30 100.0% 945 239 72 189 27 Overseas Nghi Son Refinery |Nghi Son *1,2 200 105 and Petrochemical (Thanh Hoa, Vietnam) LLC *1 Capacity before equity ratio reflection 200 *2 Yamaguchi refinery is scheduled to stop operation by the end of March 2024. idemitsu 80 60 105 80 35.1% Copyright Idemitsu Kosan Co., Ltd. All Rights Reserved. 58 59

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