Seong Hae-seong wakes from a nap on the rooftop of his high school and find that it's no longer 2005, but 2017.

Hae-seong's return elicits a warm welcome from his friends; his brothers Seong Hae-cheol and Seong Yeong-jun are less receptive.

Jeong-won is in a sticky situation with Min-jun; Hae-seong needs Yeong-jun's help with a patient.

Hae Sung looks for ways to figure out what happened to him when he accidentally runs into his high school friend, Ho Bang. Ho Bang visits Hae Sung's tomb every year with the rest of Hae Sung's high school friends. It turns out that Hae Sung was killed on his birthday.

Hae Sung finds out from Jung Won that Young Jun wasn't with her on the day Hae Sung died. The police report was recorded falsely and Hae Sung thinks it's strange. Meanwhile, Tae Hoon, who is the vice president of a department store, tells Hae Sung that Young In works in the department store. Hae Sung meets Young In, only to find out that she's been living a hard life.

Hae Sung applies for a position at Min Joon's restaurant and he has to come up with a new menu to pass the test. Meanwhile, Seo Won visits Min Joon's restaurant with her colleague who used to go to the high school that Jung Won went to. Min Joon learns that Jung Won suffered a lot because her boyfriend died in high school.