The female protagonist of the series. A beautiful young woman in her mid-20's, Hae-Young teaches mathematics at Arim High and also acts as the homeroom teacher for class 3-2. She lives with her sister and niece in an apartment block quite close to Jin-Ho's. Her father's unexpected departure from her life when she was young has had a huge impact on her. Even though she is extremely attractive and was apparently popular (and pursued) throughout her school life, she has become very guarded around men, feeling unable to trust or form relationships with them. Consequently, she is still a virgin and even shares her first kiss with Jin-Ho during the course of the story. She also seems to be following her mother's career path: she was also a teacher and became the district superintendent before retirement.There have been several instances where she acts rather childishly. In one instance, she takes out her (misplaced) anger on Jin-Ho after being reminded of her absentee father by a news article, and she repeatedly slapped him hard enough to give him a nosebleed because he didn't think he should apologize for a prior incident. Despite Hae-Young trying to be strict and meticulous in her work and home life, she has found herself in increasingly compromising and desperate situations with Jin-Ho. Much to her own initial displeasure and continuing discomfort, she finds herself developing increasingly romantic feelings for him, so much that during the course of the MT trip, they kissed several times.