Tri*Color ~3-tsu no Hajimari no Ohanashi~

The hero is an average introverted student, like you might find anywhere.
There are three girls that he likes, but he isn't proactive. Each day he just yearns from afar.
One is a young lady he sees every day on the train to school.
One is a younger cute girl who goes to his library.
One lives next door. She's his neighbor's wife.

[From DLsite English]