Ai Shimai Tsubomi... Kegashite Kudasai

The sister of Miyatsuji Kotono and Suzuyo went to the Ikaruga High School where her mother Kasumi acted as a leader of the trustee. The two beautiful girls adored Kaneshiro Shoichi. However, he gave his concern only to the school doctor, Morisawa Maiko, and he was captivated by her body.
Because he would be expelled from school if he didn’t pass the examination, he was tempted by Maiko to break into the principal’s office, and stole the disk that contained the examination.

[From AniDB]