Jessica Jung, currently 22 years old, is waiting for her boyfriend, Siwon, to come back from his 2 year military service. Jessica marks off her calendar each day he's away and it's about 3 months until Siwon's arrival home. Lee Donghae, 26 years old, was in a car accident and his body has been lying in a coma ever since. Since then, while his body is rendered completely useless, his spirit roams free, walking around the streets of Seoul. Jessica runs into Donghae, but the two find it strange as Jessica is the only person who can see him. Despite criticisms, accusations of talking to herself and being strange, Jessica continues to spend time with Donghae. As they grow closer, they remedy each other's loneliness as well as discover a heart-wrenching solution that explains their strange connection to one another.