Skirt no Naka wa Kedamono Deshita

There's a beast under the skirt, A wolf in women's clothing (スカートの中はケダモノでした) is a Japanese manga series written by Hanamaluo. A short-anime adaptation aired from July 3 to September 18, 2017, with the uncut version aired on AT-X.

Plot
Shizuka Kominami is a shy college student who, despite her bashful demeanor, attends a college mixer. There, she meets Ryou Kirishima, a beautiful, confident woman whom she quickly befriends. After leaving the mixer together, the two spend the night talking and drinking. But when an inebriated Shizuka ends up at Ryou's apartment, one thing leads to another, and she finds herself being seduced by her new friend. And what's more, Ryou is actually a crossdressing man!