簡(jiǎn)介：One day, a 29-year-old man traps as a 19-year-old young student, an extra character inside the novel that his ‘Sunbae (Senior)’ was writing and receives a mission—to make Cha Yeonwoon happy within 300 days—otherwise, death will be his penalty. Will he be able to survive, to protect his loved ones and fulfill his mission…