if you dare to cheat on me, I will change, the next one will always be better

Unwillingly dragged into a dark underworld full of secrets and mysteries, a girl names Kira will try to balance her life between the unknown and forbidden love. Will she gather the strength to surmount her deepest fears and unearth the well- kept secret of mankind? There's no turning back...

The boy who cannot use magic was Leo. He can'gt use magic for 17 years because he got cursed by a witch when he was born. And now, he's 17, he has a bodyguard named Hinata who will protect Leo from any harm. Just to protect Leo, she must follow him everywhere.

Tender and adorable bottom author × Incredibly scumbag and sentimental top

Because it's an exception, hence the preference.