Kotosaka, a green parrot with light blue eyes and darker green tail feathers, features a thick red band encircling his grey beak. His eyes radiate a bright green glow while channeling communications for Nagare Hisui. Boasting human-level intelligence, he operates as both a Green Clan member and Nagare’s foremost conduit for issuing commands.

His personality blends natural parrot mimicry with a sharp-tongued, mischievous streak, frequently indulging in cruel antics like delighting in electrocuting Neko during clashes. He emerged as a survivor of the Kagutsu incident, an ordeal that culminated in his Green Clan initiation after defiantly biting Nagare’s nose—an act cementing his status as Nagare’s inaugural clansman.

During the Mihashira Tower Incident, Kotosaka spearheads tactical maneuvers under Yukari Mishakuji’s orders. Charged with neutralizing Neko’s illusory "Cat Mountain," he successfully dismantles her powers until halted by Izumo Kusanagi’s fiery barrier. Later, Nagare deploys him to command Yukari to stand down following Anna Kushina’s rise as Red King.

Kotosaka wields Green Clan-aligned abilities, channeling their aura to generate combat electricity and shift into intangible states for bypassing physical barriers. Maintaining his position as a key operative within the Green Clan’s hierarchy, he reliably executes Nagare’s strategic directives, his role persisting without significant personal evolution across documented events.