マーシャルエイジ

Masahito is a Japanese teenager who studies martial arts. However, instead of studying, he prefers to chase pretty girls. Finally, after a quarrel with his father, Masahito leaves his home. Accidentally, he bumps into Keiko Yashima, the principal of Yuai girls school. She tests Masahito in combat, and against all rules, accepts him as the only male student in the school. Naturally, our hero uses this opportunity to "get lucky" with his all-female school mates...

[From Moby Games]