One of the very skilled examinees taking part in the JCC transfer exam in order to become an assassin. Mafuyu is a germaphobe, going to extreme lengths to avoid dirty things and reacting with incredible disgust whenever he gets dirty. In fact, he won't even use his hands in battle due to not wanting them to get filthy, opting to use blades hidden inside his shoes in order to fight. He is the younger brother of Natsuki Seba.