Ryuuji Azuma

Ryuuji used to be a competitive swimmer at the world level. He was considered one of the best and was a rival of Mikhail Makarovich, Rin Matsuoka's coach. Ryuuji also used to attend Iwatobi High School and was swimmer for the Iwatobi Swim Club. Gou Matsuoka gave him the nickname "Perfect Kinniku (Muscles) Handsome Azuma" when she found of picture of him with his old swim team. He retired from competitive swimming suddenly and is now Haruka Nanase's coach.

(Source: Wiki)