Skirt no Naka wa Kedamono deshita.

Kominami Shizuka is a mild-mannered college student who is having trouble adjusting to city life. One day, she meets Kirishima Ryou, another student who projects the image of a cool older sister. The two hit it off, but Shizuka is shocked when Ryou attempts to seduce her. Shizuka initially assumes that Ryou is a lesbian, but Ryou is in fact a man who dresses like a lady.

(Source: Crunchyroll)