Observing my mother’s friend’s son

Se-i Lim visits Taeseung Mall with her mother, Hyejeong, where they encounter Myeonghyeon, the mall’s CEO. During their meeting, Myeonghyeon asks Se-i to tutor her son, Seunghyo. However, things take an unexpected turn when Se-i accidentally walks in on Seungju, Seunghyo’s older brother, while he is naked. Shocked and embarrassed, Seungju accuses Se-i of being a pervert, though Myeonghyeon refuses to believe his claim. Seungju insists that Se-i is the only person who has ever seen him in such a state, which leaves Myeonghyeon puzzled and even wondering if her son might be gay. Worried, she asks Se-i to quietly observe and investigate Seungju over the course of three months. Will Se-i be able to uncover the truth?