Namiki Kohei (Hidetoshi Nishijima) is an ordinary security guard. He is about to turn 40 and his emotional life is blank. His only hobby is astronomical observation. He once dreamed of becoming an astronomer, but the tight financial situation at home forced him to give up this ideal. During a job, Kohei met a Korean national idol named Han Yuna (Kim Tae-hee), who was the client he wanted to protect. According to the contract, Kohei needs to provide close protection services day and night for up to 99 days. What kind of story will happen in these 99 days? As time goes by, Kohei finds that Han Yuna, who seems sunny and cheerful on the surface, has a secret hidden in her heart. The two who disliked each other at first also fell in love with each other over time. However, work is work, and no emotions are allowed. Seeing that the 99-day deadline is coming, what choice will Kohei make?