Joon is returning home from solo activities in Japan, but his plane is running late. Mir falls asleep for waiting so long, but is woken up by Seungho with terrible news. 

Mir is feeling a bit down about his body, so he decides to hit the gym with Joon. When they arrive, Joon finds that his personal trainer is away. Just as Mir and Joon are about to start training, they are met with a 'subsitute' personal trainer named 'Kyul Changmi' (Rose Mandarin) Mir instantly suspects her of something, and tries to tell Joon, but he won't listen. What will happen in the end?