Aida ni Hatachi

Takae Reona is 3rd year high school student who will soon be taking college entrance exams. One night, he encounters a beautiful woman named Misa, and immediately falls for her. There's just one catch: she's actually 38 years old. Worried about the 20 year age gap between them, Reona takes on the identity of his older brother, but it ends up he's not the only one who's hiding something...