A subordinate of Baek-tong, the boss of the East Wing, serving as his right-hand man (or rather, right foot). She is 18 years old. Female. Height is in the late 170s cm. She wears a reddish-brown H-line skirt with black stockings and a tight-fitting black long-sleeved turtleneck. She has sharp, upturned eyes with black pupils and long black hair with exposed forehead. She controls Classes 3 and 4, which are the eastern territories. There are many of Retril's subordinates in Class 3, so she is said to overlook tax collection there. Given that she is often in the counseling room, it seems to be her base of operations. Due to her mysophobia, she hates dirty things and always wears nitrile gloves, and she uses weapons rather than bare fists when fighting. She refers to overpowering and teaching someone by force as "education." She views fighting someone as educating them. When she sees a student acting insolently, she thinks they need education. She feels like her circuits are purely fried. A screw is loose in a completely different dimension. She manages a ledger containing all sorts of collection lists. She has set a front gate usage fee, collecting money from everyone who enters the school through either the front or back gates. If they cannot pay, they are recorded in the ledger and become debtors. A vicious cycle continues where the kids who have accumulated debt in this ledger tear each other apart. She offered to exempt Hari-chae—who used to beat up and kick out upperclassmen demanding taxes—from taxes until graduation, and she won the fight against Hari-chae. Since then, she has made Hari-chae her direct servant. She doesn't point out whether Hari-chae uses informal language, swears, or whatever her tone is. She doesn't try to fix it and doesn't care. Rather, she just thinks it's typical of Hari-chae. She only responds to the fight if Hari-chae attacks her. Because of her mysophobia, she makes Hari-chae clean the entire school. She is particularly sensitive about bathroom cleaning, so she is the one who made Hari-chae guard the bathroom and collect tolls to prevent anyone from entering and making it dirty in the first place. Retril only calls Hari-chae by her name without a surname. Whenever she's bored, she calls Hari-chae and treats her like a clown. She calls only Hari-chae and no one else. Clean where you already cleaned, wipe where you already wiped... Feeling spiteful, Hari-chae attacks her every time, but she has never beaten Retril. The difference in strength between the two is overwhelming, so Hari-chae experiences defeat every time. She has femdom tendencies. Of course, she herself is not aware of it.