So basically a college student(a boy), have crush on this girl who was his college classmate.

He does not have courage to confess to her, and just holding it. Somehow something happened, a girl with green hair come to meet him and tell him she come from another world, a parallel one that nearly the same as his world with different "twist".

the green haired girl tell the guy that he was dating his crush on her "another" world and the guy did not believe it but the girl shows him the proof and he believed her.

now the guy try to win his crush heart , thinking he have the chance , while also curious why this girl suddenly appeared in first place to his side.