Kai "Arlong" Asui was once a middle schooler, until he got enrolled into U.A. for singlehandedly apprehending Dabi with just his sheer strength. Believe it or not he is the younger brother of Tsuyu Asui. Though they are not biologically related and he was actually adopted into the family when he was just a baby. However him and Tsuyu love each other as if they were true siblings. Kai exercises almost every day for four hours non-stop each day. He is currently twelve years old.