Nyotai-ka Yankee Gakuen☆: Ore no Hajimete, Nerawaretemasu.

Torao is a delinquent who's always eager to let his fists do the talking. His greatest enemy is Ryouhei, both the strongest guy in school and a terrible womanizer. When Torao tries to get revenge for the time Ryouhei humiliated him in a fight, his plans are thwarted by a mysterious potion that turns him into a girl. From that point on, Torao (now Torako) develops a steamy and complicated relationship with the boy he hates! But, is hate really the only thing on Torao's mind?!

(Source: Renta!)