The Treasurer for the student council. He's an unusual case of being an elite Fox. He was brought to the Bon-Ga at the age of 10 unlike other Foxes who were born at the Bon-Ga. Sa-Eun is also the one responsible for finding Yu-Da and taking care of him. His personality is rather stern but he does crack a smirk/grin here and there. He takes his gaurdian duty seriously over Yu-Da since they live in the same house.
His powers are considerably strong too since he's an elite Fox. He can wield a sword quite well, use some magic, and isn't afraid of crashing into people's apartments. Sa-Eun is a smoker so along with his cigarette comes a perveted imprisoned smokey soul named Moky-Moky.