Nanjou Terumasa♂

Nanjou is Kinzou's personal physician and close friend. He is also Kinzou's opponent in chess. He is one of the few people Kinzou, who has grown fanatical in his suspicions, opens his heart to. He has a bighearted disposition, and has come to the island for a long time, never getting upset by Kinzou's hot temper. He owned a clinic on Niijima, the island closest to Rokkenjima, but he resigned in favor of his son Masayuki.

[Edited from Wikipedia]