Height: 175 cm
Dominant Hand: Right
Play Style: Counter-puncher
Special Move: Moon Volley

Seishun Gakuen 3rd Year Class 2. Oishi is the vice-captain of Seigaku Tennis team. He is a worry-wart and is much concerned with other people's welfare, thus erning the nickname "Seigaku's mom". He plays doubles with Eiji Kikumaru and their tandem is called the Golden Pair.