The 23-year old Japanese midfielder enjoyed an impressive debut campaign with Der Club last season, scoring four goals and providing 11 assists, following his move from Cerezo Osaka.
"He arrived in a very different country, with great expectations, and hit the ground running,” Bader said.
"It sounds like it all happened really easily, but a young player like him is going to go through a period of adaptation.
"We hope that with the signing of Makoto Hasebe, he'll find he's got even more support both out on the pitch and away from it. He's a very important player for us, one who can make all the difference."