Kaishu Sano was born on 30 December 2000 in Tsuyama, Okayama, and signed his first professional contract with Machida Zelvia in 2018 — at the time a J2 club. After four seasons developing at Machida, he moved to J1 side Kashima Antlers in 2023, where he was an immediate starter at defensive midfield, registering 26 J1 appearances with a goal in his debut season.
In summer 2024 Sano made his European move to Germany with FSV Mainz 05. The transition was extraordinary: he was an everyday Bundesliga starter from his first match — 34 league appearances in 2024–25 and 32 in 2025–26 (with 1 goal, 2 assists). He has since added a goal and an assist in 11 UEFA Europa Conference League matches, proving he can perform at the European stage as well.
A combative, ball-winning defensive midfielder with the energy to cover ground from box to box, the technical security to play out from deep, and growing goal-scoring contributions, Sano has emerged as one of the most exciting central midfielders in the Japanese game.
He earned his Japan A-team debut in 2023 and started friendlies through 2024 and 2025. As Wataru Endo and Hidemasa Morita continue to anchor the senior midfield, Sano is the most natural and immediate successor at the No. 6 — one of Japan's clearest succession plans heading into the 2026 World Cup.