The Hypnosis

Do Hyun, a college student and his friends have lost their childhood memories and they are living their lives in their own way. One day, Do Hyun is introduced to Jin Ho who lost his parents in an accident as a child. Do Hyun's friends also heard Jin Ho's story and they decided to become Jin-ho's friends. In the meantime, Do Hyun gets interested in hypnosis that Jin Ho receives to treat his trauma due to an accident and he tries to do it. Since that day, Do Hyun and his friends keep experiencing strange things and they all feel to have been hypnotized as recollecting memories of Seung Min, who was with them at a nursing home when they were young but already dead. Who hypnotized them and why did the memories of Seung Min come back?