Kotaro Arima is a Japanese forward born in Ibaraki on 3 September 2000. He developed in Kashima Antlers' youth teams and entered the senior squad before loan spells at Tochigi SC. He then moved to Iwaki FC, where he became an important attacking player and scored regularly, including a productive 2024 season. In 2025 he joined Oita Trinita and continued his career as a centre-forward in J.League football.