Omegaverse

Special Alpha [Seme] x Beta [Uke] ; Alpha is trying to turn the Beta into an Omega and claim him for himself.

Interesting take; Alpha's turn into demon's and our Omega can as well when normally they can't.

Mc [Beta] regresses in time and proposes a contract of marriage with major benefits to the ML [Alpha-Dominant] in order to protect his younger sibling for 3 years so that he can safely obtain the legacy in their blood to be able to protect himself from harm.