Lee Donghae is a young caretaker working at Sunny Days Addiction Correction Facility, or SD for short. All the other caretakers find his methods of helping patients just a bit odd though. The lonely 21-year-old never notices when they whisper behind his back though and continues doing what he loves, helping other people. His whole life gets turned upside down though, with the arrival of new doctor, Lee Eunhyuk.