School Days(2006)

Makoto Ito rides the train to and from school every day. However, at the beginning of his second term, he falls in love with a beautiful girl that also rides the train. Unfortunately, she barely knows of his existence. Her name is Kotonoha Katsura, and though they attend the same school, they are not in the same class. In an attempt to catch her eye, Makoto enlists the aid of a close female friend of his: Sekai Saionji. She helps him, despite the fact that she—unbeknownst to Makoto—is in love with him. Thus the three are bound in a love triangle of life-changing proportions.

(Source: Anime News Network)