Ao Tanaka was born on 10 September 1998 in Kawasaki and came through the Kawasaki Frontale academy alongside Kaoru Mitoma — a decade in the same youth system before stepping up to the J1 first team. He won three J1 League titles with Frontale (2017, 2018, 2020), the J.League Cup in 2019, the Emperor's Cup in 2020–21, and the Super Cup twice, establishing himself as one of the most reliable young midfielders in Japan.
In summer 2021 he moved to Germany with Fortuna Düsseldorf, initially on loan and then permanently. Across three seasons in 2. Bundesliga he scored 12 goals in around 90 league appearances and earned a reputation as a midfielder who could carry the ball, defend with intelligence and contribute on the scoresheet. In August 2024 he joined Leeds United in the Championship — a step into a more physical, higher-tempo league. He made it look easy.
Tanaka's first season in West Yorkshire was outstanding: 43 league appearances, 5 goals and a Championship title that returned Leeds to the Premier League. In 2025–26 he stepped up again, scoring twice in the FA Cup and twice in the Premier League while becoming an indispensable starter under Daniel Farke.
A box-to-box midfielder with strong defensive reading and the calmness to receive in tight spaces, Tanaka has been a Japan regular since 2021 and started at the 2022 FIFA World Cup, where his composure on the ball was central to Japan's high-pressing system.