Momo Chiyoda is a fifteen-year-old high school student attending Sakuragaoka High School. She is the town's resident magical girl, associated with the Light Clan and themed around peaches and the color pink. Momo was adopted at a young age by an older magical girl named Sakura Chiyoda, who served as both a maternal figure and a mentor in magic. Momo does not know her biological parents and suspects she may be an orphan. Her career as a magical girl is shrouded in mystery, and there are rumors that she once saved the world. She later considers herself a self-proclaimed retired magical girl.

On the surface, Momo presents a calm, cool-headed, and stoic demeanor. In reality, she is socially awkward, lazy, and prone to embarrassment and pettiness. She holds long grudges and takes criticism to heart, yet she is fundamentally kindhearted and fiercely loyal to those she cares about. She has a strong passion for muscle training and physical strength, to the point of being called a maniac about it. This enthusiasm can make her hotheaded or inclined to believe that every problem can be solved through sheer force. She is also terrible at cooking, relies on convenience store meals, and shows little interest in household chores or academics despite being intelligent. She has a secret fondness for cute things, such as cats and a local mascot character, though she rarely admits it and tends to avoid or deflect any conversation about herself.

Momo's primary motivation shifts over time. Initially, she is simply fulfilling her duty as a magical girl protecting the town of Seiiki Sakuragaoka. After encountering Yuko Yoshida, a demon girl who tries to defeat her to lift a family curse, Momo takes pity on Yuko and decides to train her instead. Her motivation becomes helping Yuko grow stronger, forming a genuine bond with her, and gradually rediscovering reasons to enjoy life beyond her lonely, duty-bound existence.

In the story, Momo serves as the deuteragonist and the initial rival to the protagonist Yuko. Their relationship begins with a failed duel, quickly evolves into an unlikely friendship, and deepens into a sisterly bond as they learn about their intertwined past. When Yuko becomes trapped in her own memories, Momo temporarily converts to the dark side to enter those memories and rescue her. Momo also shares a close, supportive friendship with Mikan Hinatsuki, another magical girl who eventually moves into the same apartment complex to be near Momo and Yuko. Her classmate Anri Sata affectionately calls her Chiyomomo.

Throughout the series, Momo undergoes significant development. She starts as a joyless, emotionally isolated figure who floats through life without close connections. As she spends more time with Yuko and breaks out of her shell, her true personality leaks out more openly. Her public facade shifts from a perfect, cutesy magical girl to a more cynical, careless, and delinquent-leaning individual. She becomes more expressive and emotional, though she displays these vulnerable traits only with those she trusts.

Momo possesses extraordinary physical power that overwhelmingly surpasses that of normal humans, even without transforming. She can stop a moving truck with one hand, lift weights designed for large muscular men, and handle a giant tire meant for mining trucks with ease. Her transformation into her magical girl form occurs in a fraction of a second. Her magical girl weapon is a heart-shaped staff, and her signature attack is called Fresh Peach Heart Shower. She later obtains a fallen form after temporarily becoming Yuko's vassal, which includes a black katana and a different outfit. Despite her immense strength, she is considered the weakest among the other magical girls of the Light Clan.