Hametsumachi Akuyaku Reijou wa Zetsurin Kikoushi ni Dakitsubusareru: Komitsu Konzen Koushou

I was reincarnated in another world as Serena, the villainess. If I'm going to be ruined anyway, I might as well do it my way! I unleashed my tomboyish spirit from my previous life and became incredibly successful with my newly awakened cheat-like athletic abilities. However, my fiancé, Roberto, with whom I thought we had a cold relationship, suddenly became intensely possessive!? I'm not good with typical perfect noblemen, but in Serena's body, I can't resist the pleasure...! I'm loved every night and kept captive at this boarding school—!?

(Source: Taiseisha, translated)