Mark was diagnosed with Ewing Sarcoma when he was thirteen years old. He's been treated in the hospital for four years now, but there is little the doctors can do to treat him. Donghyuck was twelve when he found out he had Non Hodgkin Lymphoma. He shares a room with Mark, and has been for four years now. They both know they're going to die sooner or later, that's why Mark can't understand why Donghyuck seems so happy and free.