Welcome to demon school Gojo-kun

Gojo is the grandson of Sullivan and a very powerful demon. At a young age he was abandoned by his family to be raised by his grandfather though he didn't care. For he loved his grandfather and his servant Opera but months went by and he began to be lonely so Sullivan did something unexpected. He got him a little sister named Irumi. So basically Sullivan bought Irumi from her not so great parents, which Gojo can relate since he to was abandoned by his parents. At age 16 Irumi was finally ready to go to Babyls and join her older brother.