The Demon Lord's Exclusive Pet, the Little Demon Concubine

At the beginning of time travel, he was actually a useless slave? What the hell? ! Too thin? Are you kidding? Look at me transforming into a master of physical skills in seconds! Can't you practice magic if you can't sense spiritual power? Stop making trouble, absorb magic and become a peerless master in minutes! But who can tell her what's going on with those tails behind her? And what kind of look does that dark, domineering and cold prince have in his eyes...