Myungha Tae is going to die in 300 days. Well… maybe. After getting sucked into his friend’s novel, "Love Interest Zone," 29-year-old Myungha becomes a 19-year-old high schooler again with one mission—make Yeowoon Cha happy or die. With only 300 days to succeed, Myungha must break past Yeowoon’s barriers and prevent him from experiencing the same tragic fate as he did in the novel. But with Yeowoon’s favorability toward him in the negatives, will he be able to survive?