School days manga

School Days summary:

The story revolves around a love triangle between the male protagonist, Makoto, and two girls in his year, Kotonoha and Sekai. Makoto develops an interest in Kotonoha, and although they both take the same train to school, she seems to be unaware of his existence. One of his classmates, Sekai, gets the two together despite holding strong feelings towards Makoto.