Momoko Asahina is a first-year student at Seio Gakuen and a member of the Light Music Club, where she plays the keyboard. She began learning piano at a young age under the influence of her music-loving parents, which laid the foundation for her musical ability. Her family runs a liquor store, which is located next door to the soba restaurant owned by the parents of Yuzuko Hazuki, her childhood friend. Momoko has known Yuzuko since kindergarten, and the two have remained close friends ever since.

Momoko is characterized by her warm, honest, and openly supportive nature. She is a genuinely kind person who cares deeply about the well-being of those around her and is always ready to lend a hand or offer encouragement. Her trusting disposition, however, also makes her somewhat naive, as she rarely doubts others and can be easily deceived. She is described as being very honest and straightforward, which contributes to both her charm and her vulnerability. Within the Light Music Club, she has a particularly close friendship with Nagiko Kurokawa, who is the bassist of the all-girls' band Neuron★Cream Soft. Momoko plays the keyboard for this band, contributing to the group's musical performances.

Her motivations are largely centered on supporting her friends and enjoying her time in the club. She derives satisfaction from being helpful and from participating in group activities, particularly music. Her role in the story is that of a supportive and cheerful friend within the larger ensemble of characters. She does not undergo a dramatic personal transformation, but her consistent reliability and good nature make her a steady and likable presence among her peers. Her notable abilities include her keyboard and piano skills, which she uses as part of the band. She is also recognized for her energetic and friendly personality, which helps bring people together and maintain harmony within her social circle.