The girl in my class which I fell in love with... was in love with someone else.
However, that someone else, was a member of her own family.

A trivial encounter leads the protagonist to developing feelings for a girl in his class.
While having become aware of his love for her, he cannot muster up the courage to confess,
and ends up remaining friends with the girl.
However, one day he witnesses her together with an older man...

That is the kind of story being told here.

Official Translations:
English, S.Chinese, T.Chinese