The principal characters of Masks by Fumiko Ueda (who published under the name Fumiko Enchi) are:

Tsuneo Ibuki: He is a young academic and a professor of literature at a university in 1950s Japan.

Toyoki Mikamé. A doctor, he is about the same age as Ibuki and is a close friend of his.

Yasuko Togano. A young widow whose husband Akio was killed in an avalanche on Mt. Fuji.

Mieko Togano. Akio's mother, Yasuko's mother-in-law. She is the editor of a poetry magazine and is an expert on literature of the Heian period (794–1185 CE), especially the famous Tale of Genji.

Harumé Togano. The twin sister of Akio. She is mentally challenged and is kept largely in seclusion. In the story, her mother Mieko uses Harumé in a plot to manipulate Ibuki, who (along with his friend Mikamé) is in love with Yasuko, Mieko's daughter-in-law.

Yu. Mieko's housekeeper and nursemaid to Harume.

Sadako Ibuki. Tsuneo Ibuki's wife.

Masatsugu Togano. Mieko's husband, deceased at the time the story begins.

Aguri. The maid who was Masatsugu's mistress while he was married to Mieko.

Mieko's lover. The actual father of Akio and Harume. He died while serving at the front in World War II.

Dr. Morioka. A friend of Mikamé who relates to him the details of a miscarriage Mieko had suffered in her first pregnancy, which was caused by Aguri.