Isuzu Ichinose, the older brother of Subaru Ichinose, enlisted young in the Earth Federation Army. His exceptional skill led to a rapid rise and flourishing military career, yet fundamental differences with its principles and ideological disagreements ultimately drove him to leave. He defected to the rival space immigration organization, People of Metus (or Metus People), where he attained an executive-level position.

This defection placed him directly against his younger brother Subaru, a pilot for the Earth Federation aboard the space battleship Tiramisu, creating a central sibling conflict representing opposing sides. During the narrative, Isuzu reunites with Subaru after Subaru temporarily abandons his post and defects to People of Metus. However, their reunion is brief; Subaru ultimately returns to the Earth Federation due to a perceived trivial grievance.

Physically, Isuzu possesses dark blonde hair and cyan eyes. He stands 1.80 meters tall, weighs 62 kilograms, has blood type B, and a birthday of June 19. Within People of Metus, he holds the rank of Taisa (Colonel) and serves as both a pilot and a captain.