Ochikobore Majo no Shoutai wa, Seieki (Maryoku) wo Kate to Suru Saikyou no Akuma deshita.

In a world where magic is an everyday fact of life, just about everyone is able to use it... Well, except Luca... She has to rely on her older brother Glen and the young beastman Abel. She's still trying, though, because her goal is to be as great a witch as her incredible mother.
One day, a mysterious, black-robed witch claiming to be an acquaintance of Luca's mother gave her an unusual fruit... "Take a bite and your true powers will awaken." And Luca did just that. The moment she did, however, something strange happened to her body. That's how Luca discovered she was the daughter of an incredibly powerful demon. The fruit undid the seal her mother had placed on her powers, causing her magic to run wild and endanger her life. The only way to save her was to pour semen (magical energy) into her body, neutralizing her own energies. And so, in the spirit of charity, Glen and Abel had sex with Luca. A sweet scent exudes from her newly-empowered body, and the two men are helpless to resist. Which is good, because she's going to need a lot of energy at all times of day to keep her powers in check!