Kōta Inokuma is the younger twin brother of Mitsuki Inokuma and the younger brother of Yōko Inokuma. A fourth-grader during the anime's second season, he possesses light brown hair with a reddish tint and brown eyes. His typical attire includes layered shirts, shorts, sneakers, and socks, and his appearance resembles Yōko more closely than Mitsuki.

Generally quiet and reserved, Kōta shares his twin sister Mitsuki's frequent tendency to fabricate fictional or exaggerated stories. Despite this habit, he displays care and understanding towards Yōko, such as comforting her when she accidentally damaged Mitsuki's teddy bear.

Within the narrative, Kōta functions primarily in a supporting capacity, often seen alongside his twin. His interactions sometimes provide minor assistance to other characters, like indirectly helping Aya Komichi navigate her feelings for Yōko. Kōta maintains a consistent background or minor character role throughout all official media, including the television series, the "Pretty Days" OVA, and the "Thank You!!" film.