An expelled boxing champion, who now is a high-school teacher, witnesses intolerable violence and throws her first punch to build justice against it, while putting on a mask.
On the afternoon of the day before her school trip, Se-mi wakes up from her strange dream and heads to her Ha-eun. It was because she felt like she had to convey the feelings she had been holding back for a long time today. However, unlike her overflowing heart, the two keep falling apart.