Momosuke Oikawa, who prefers to be called Momo, is a 15-year-old male member of the cross-dressing idol unit POP'N STAR. Standing 154 cm tall and weighing 44 kg, he was recruited by Kokoro Hanabusa. Despite his role, Momo remains unaccustomed to feminine attire, often forgetting his skirt and lapsing into male pronouns or boyish postures like sitting with legs open, prompting Kokoro to remind him about the unit's image. He becomes upset if called "Momosuke" against his preference.

He has an unnamed father, mother, and younger brother. Kokoro gave him a stuffed brown squirrel toy named Ricky to establish his idol persona. Momo possesses a fluffy appearance and emits a naturally soothing aura. His hobbies are gardening and eating; the school granted him a dedicated flower bed due to his consistent plant care. He exhibits a substantial appetite, favoring gyūdon and disliking crab. He is skilled at making crepes, specifically preparing them for fellow unit member Runa Kagurasaka.

Initially hesitant about cross-dressing and idol life, Momo gradually developed respect for Kokoro's diligence and admiration for Runa's reliability, recalling how Runa helped him when he tripped during their first meeting. While some feminine behaviors are performed intentionally for the producer and Kokoro, his love for flowers is genuine. Before becoming an idol, he aspired to be a florist but believed it was an unattainable profession for boys.

Momo intentionally displays aggression on occasion, though he generally maintains a healing presence. His journey reflects growing camaraderie with his unit members despite initial reluctance as he balances personal identity with idol responsibilities. His birthday is January 23 and he has AB blood type.