Callisto is the typical quiet boy stereotype. He doesn't talk to anyone except Nienne- mainly because she refused to let him keep alone all of the time. He's a class 1A student and the only student who questions and even looks down on Alcyone. He has a twin sister named Calica.

Quirk : Can turn the room/up to 100 feet in front of him into total darkness. If he uses his power too much, he will go blind for 5 minutes.