Looking for a manga where this girl and boy are pretending to be girlfriend and boyfriend. I think they are supporting characters in the manga. There is this scene I remember, in the rooftop, the girl asked him why did he not clarified that they were just pretending when he was asked by a girl in the cafeteria. He said there's no need for them to be corrected, let them think what they want. They are already falling for each other by then.

Is it Kanojo, Okarishimasu ?

Sounds like a scene from Horimiya if it’s the supporting characters who were fake dating