7-kakan Gentei Kanojo

A yuri romantic comedy centered on a temporary relationship between a gal and an honor student.

The story begins when Manatsu, a gal who is on the verge of repeating a grade, starts receiving tutoring from Sumie, an honor student. Manatsu loves shoujo manga and romantic gossip but has the vague that having a boyfriend somehow doesn't fit her. When she casually brings this up, Sumie suggests, "Why not try starting with just the form?" and offers "How about dating me for just seven days?"

(Source: MangaDex)