Investor Presentaiton

Basic Chemicals Segment Business Overview as of the end of March 2023 [mil tons/year] Production Capacity for core products Operating Company Complex/Factory/Refinery Ethylene Para-Xylene Mixed Xylene Styrene Monomer Equity Ratio Japan Idemitsu Kosan Chiba 0.374 0.265 0.210 Aichi 0.357 0.170 Tokuyama 0.623 0.214 0.340 Showa Yokkaichi Yokkaichi 0.518 75.0% Sekiyu Seibu Oil Yamaguchi 0.250 100.0% Total 0.997 0.836 0.938 0.550 Overseas Idemitsu SM Pasir Gudang (Malaysia) Sdn. Bhd. (Johor, Malaysia) | Nghi Son Refinery Nghi Son 0.700 and Petrochemical (Thanh Hoa,Vietnam) LLC Total 0.700 idemitsu 0.240 70.0% 0.240 35.1% Copyright Idemitsu Kosan Co., Ltd. All Rights Reserved. 59

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