Masa san
Name in Japanese
Rōmaji Translation Masa
Appears in Anime
Voice Actor (Japanese) Katsuki Murase, Shūichi Ikeda (young Masa Shiranui)
Voice Actor (English) Christopher Sabat (English)
Personal Info
Gender Male
Affiliation Seto Group

Masa ( Masa?) is a member of the Seto Group and is Gozaburo Seto's right hand man.


Masa is a tall, muscular man and he has a Afro. He also wears a suit and tie mostly throughout the series and is always seen wearing sunglasses.


Masa is the only one apart from Ren Seto who does not object to the engagement and sometimes even gives advice to Nagasumi. Usually he is portrayed a silent man but due to his highly good looks he mostly captures peoples' hearts such as making Nagasumi's Mother fall for him just by looking at her and even making Nagasumi admire him. However, when he drinks he tends to talk too much and reminisce. Masa cares a lot for his sister Akeno Shiranui and is very protective of her often beating up those who are aggressive towards her. 


Masa also transfers to Nagasumi's school, becoming his math teacher (whose word problems tend to describe to the mathematical aspects of underworld gang operations). There is a running gag of Nagasumi displaying an attraction towards Masa since their "first kiss" in the first episode. He is revealed later in the series to be the long-lost brother of Akeno Shiranui.

Powers and Abilities

Masa is one of the few Merfolk not afraid of cats, explaining that he decided to overcome the fear as a child.