Choppiri Toshiue demo Kanojo ni Shite Kuremasu ka?

A high school boy, Kaoru Momota, saved a high school girl named Hime Orihara as she was getting molested on the train one day. The two of them fell in love with each other, but she has a secret that she can't tell anyone. "I'm...actually 27 years old." The high school girl actually turned out to be a 27-year-old woman!
(Source: MANGA UP!)