Hatsukoi Jikan / 初恋時間.

Rin is an ordinary student who has, so far, spent his time studying rather than with love and friends. This only changes when he meets the lovely Ena, who seems to live in a completely different world. Rumour has it that she has several boyfriends at the same time and has slept with over 100 men, but she's not exactly the smartest either, which is why Rin agrees to tutor her. Soon, his lessons are crowned with success, and as a thank you for improving her grades, Ena has come up with something special for the nerd......