Career
Nagoya Grampus
Koyamatsu made his official debut for Nagoya Grampus in the J. League Division 1 on 13 March 2015 against Ventforet Kofu in Yamanashi Chuo Bank Stadium in Kofu, Japan. He started the match and was subbed out in the 70th minute replaced by Kengo Kawamata. Koyamatsu and his club lost the match 1-0.