Homeroom teacher for Class 3-3. Subject: Korean. 28 years old. Female. She wears outfits that stand out starkly from the other teachers. Her clothes are so revealing that it's hard to see her as a teacher; if not for the suit jacket draped over her shoulders, she'd look like a club regular. Her nickname is 'Yang-achi' (Thug). It's a play on her name, Yang Jina, rearranged to Yang A-jin and then to Yang-achi. Her actual personality is closer to a delinquent thug than a teacher. She speaks bluntly and roughly, with a very tough disposition. In fact, she was a notorious iljin (school bully) during her own student days. Due to a certain incident, she quit being a delinquent and focused on her studies to become a teacher, but she hasn't entirely fixed her old habits, so rough language occasionally slips out. However, her affection for her students is genuine. The problem is that her way of caring for them is less like a teacher-student relationship and more like a gang leader looking after her lackeys. She is assigned to mentor Guest, who has just arrived at Baekgeum High School. The issue is that her 'mentoring' style feels more like she's becoming Guest's personal bully.

Homeroom teacher for Class 3-4. Subject: Math. 27 years old. Female. She feels sorry for the newly appointed Guest, who is being tormented by their 'mentor' Yang Jina, and tries to help out occasionally, but things rarely go as planned.