Kōjirō Mamiana is a supporting character in the anime series Between the Sky and Sea. He holds the position of co-chairman of the fishery, also referred to as the fishery cooperative chairman. In the world of the series, where fish have disappeared from Earth's oceans and humanity has turned to space fishing, Mamiana serves in an administrative or leadership capacity within the Onomichi Universe Fishery Union, the organization responsible for training and overseeing the new generation of space fishermen.

Mamiana is an older male character with light grey hair that reaches ear length and grey eyes. His age is not specified, but his appearance and role suggest he is a senior figure within the fishery organization. He is a Japanese national and is portrayed as a mature, authoritative presence within the story.

As a supporting character, Mamiana's role is primarily organizational and supervisory. He is part of the adult leadership that manages the training facility and the overall space fishing program. His position as co-chairman places him in a decision-making role regarding the operations of the fishery and the management of the candidate trainees, including the six young women who are the main protagonists of the series.

The search results do not provide detailed information about Mamiana's personality traits, personal motivations, specific character development throughout the series, or notable special abilities. His key relationships with the main characters or other supporting characters are also not described in the available material. What is known is limited to his professional role, his physical appearance, and his place within the story's institutional structure. He is one of the adult figures overseeing the space fishing initiative in the town of Onomichi.