Grisaia no Kajitsu

Synopsis

Returning to the dorm after his morning jog, Yuuji sees Amane picking the lock to his room and immediately suspects that she may be an assassin. He listens and watches from the doorway as, to his considerable surprise, all she wanted to do is surprise him with a wake-up kiss. She then proceeds to jump onto his bed and masturbate after smelling his worn clothes. Yuuji then makes his presence known to Amane's considerable embarrassment. While rushing to class later that morning he makes up a song for Makina in which he teases Amane for her earlier actions. At lunch, Amane expresses her concern that Makina is starting to imitate Yuuji's mannerisms. That afternoon Yuuji overhears an erotic voice and discovers that it is Michiru, who is playing with a kitten. The following day, he inadvertently agrees to have Sachi make him a shark pouch (like Michiru's) only with glitter. Some quick thinking on Michiru's part allows him to foist the pouch on Makina. That afternoon during gym, Amane hurts her ankle and Yuuji carries her to the infirmary. After he treats her injury, Amane requests that Yuuji be her boyfriend. When he refuses, she changes her request to be regarded as his older sister which he agrees to. The next day, Amane and Makina share their lunch with Yuuji and he realizes that he has been avoiding people since his "master"'s death. (Source: Wikipedia)