An upper-class widow in Joseon keeps her double life as a masked vigilante under wraps — until a government official learns of her nightly escapades.

When Kang Bok-Soo was a high school student, he was falsely accused of committing violence and kicked out of school. This was caused by his first love Son Soo-Jung and a male student Oh Se-Ho. Kang Bok-Soo is a now an adult, but his life has not gone smoothly. To get revenge on Son Soo-Jung and Oh Se-Ho, he returns to the same high school as a student. The environment at the school has changed and Kang Bok-Soo gets involved in unexpected cases.

Set at a prestigious private high school in Gangnam, Seoul, South Korea. Eun-Byeol is a popular student at the private high school. She goes missing and returns, but she has lost her memory. She tries to find out the truth.