With the help of a friendly ghost, Masaki, Ono-sensei can examine his young patient's teeth without much fuss. It seems that only Ono-sensei and children can see Masaki. He brings a calming presence, which is convenient for children at the dentist and for Ono-sensei as well. But is he really a ghost? He doesn't remember much about his past but for some reason, he's very attached to Ono-sensei. So much so that Masaki hangs out around the office and even walks Ono-sensei home. Once they reach the entrance to Ono-sensei's apartment however, Masaki is asked to stay out. Ono-sensei doesn't want Masaki to know that something else haunts him behind closed doors.