On 8 March 2019, it was announced that Wakatsuki would join the team as a specially designated player for the 2019 season. It was also announced that he would join the senior team permanently in the 2020 season. He made his league debut against Vissel Kobe on 26 May 2019. Wakatsuki scored his first goal in the Emperor's Cup against BTOP Hokkaido on 7 June 2023, scoring in the 82nd minute.
Loan to Sion
On 28 January 2020, Wakatsuki was announced at FC Sion. He made his league debut against FC Luzern on 2 July 2020. Wakatsuki scored his first league goal against Servette on 14 March 2021, scoring in the 84th minute. On 28 December 2021, it was announced that his loan would be expiring and he would be returning to Shonan.