Kota Mizunuma was born on 22 February 1990 in Yokohama. He came through Sagan Tosu and FC Tokyo's youth football before joining Cerezo Osaka in 2017–18, where he won the J.League Cup in 2017, the Emperor's Cup in 2017–18, and the Super Cup in 2018. In January 2020 he joined Yokohama F. Marinos.
With F. Marinos he won the J1 League in 2022, the Super Cup in 2023, and the EAFF E-1 Football Championship with Japan in 2022. The 2023 season produced 33 J1 matches with a goal and 7 assists. In January 2025 he moved to Newcastle Jets in Australia's A-League.
The 2024 season produced 12 A-League matches with 2 goals and 4 assists for the Jets, plus 18 J1 matches with 2 goals and 2 assists at F. Marinos before the move; 2025 has been productive at Newcastle Jets with 18 A-League matches with 2 goals and 2 assists.
A 177cm two-footed right-sided creator with vision, dribbling and the goal-scoring instinct of a senior attacker, Mizunuma is one of the most decorated Japanese players of his generation. He is in the wider 2026 FIFA World Cup squad picture as a senior wide creative option.