Stuck with him. // RuiKasa Royalty x Magic User AU Fanfic

"You'll be stuck with me from now on."
Prince Tsukasa Tenma, who has been worried about his younger sister Saki's health, ventured off to seek a powerful magic user who has the ability to grant wishes. But, those wishes always come with a price. A price not everyone can pay.
And how exactly does he react when he hears what he needs to do to cure her? Not so great.
But, he reluctantly accepted the offer. After all, he swore he'd do anything for Saki.
Over time, Rui started to catch feelings for Tsukasa as the two got closer and closer. Will their feelings ever be mutual?