He has brown hair and brown eyes. His appearance is similar to Manatsu. His skin, however, is slightly lighter than Manatsu.
Masumi has also a very playful personality, and sometimes likes to dress in girl's clothing much to chagrin of his identical brother Manatsu. He is also very protective of his siblings and does his best to keep them safe when he can. And when his family is threatened, he can become serious and have a much darker personality.
He is flirtatious around Izumiko.
Masumi is the late brother of Mayura and Manatsu. He died of a heart defect while taking an afternoon nap when he was six. After his death, he become a divine spirit and only Izumiko, Mayura and Manatsu can see him.
Masumi has great spiritual powers. It is the sediment of Kuzuryuu Ookami (九 头 竜 大 神), a holy God in Togakushi, and he has the ability to devour other spirits during fights.
He also can inpersonate and replace both Mayura and Manatsu.