"Peach Girl" centers on Momo Adachi, a high school student whose tanned skin and bleached hair lead to frequent misunderstandings about her personality. Despite her appearance, Momo is kind-hearted and reserved, harboring feelings for her classmate, Toji. However, her best friend, Sae Kashiwagi, secretly manipulates situations to sabotage Momo's relationships, driven by jealousy and her own unrequited feelings for Toji. Sae spreads rumors about Momo, portraying her as promiscuous, which complicates Momo's attempts to confess her feelings to Toji.

The narrative intensifies when Kairi Okayasu, a flirtatious and confident boy, enters Momo's life. Kairi is genuinely interested in Momo and becomes a rival for her affections, creating a love triangle. Momo struggles to navigate her emotions while dealing with Sae's schemes, which escalate as the story progresses. Toji, initially oblivious to Momo's feelings, begins to question his own emotions and the truth behind the rumors.

As the series unfolds, Momo faces challenges in balancing her relationships with Toji, Kairi, and Sae. Sae's manipulative tactics grow more extreme, leading to confrontations that test Momo's resilience and friendships. The story explores themes of trust, self-identity, and the consequences of deception, as Momo strives to overcome the obstacles created by Sae and find happiness in her romantic and personal life.

The characters are central to the plot's development. Momo's journey is marked by her determination to stay true to herself despite societal judgments. Toji represents the idealistic love interest, while Kairi offers a contrasting, more assertive approach to romance. Sae's actions drive much of the conflict, highlighting the destructive nature of jealousy and insecurity. The interplay between these characters creates a dynamic and emotionally charged narrative, making "Peach Girl" a compelling exploration of teenage relationships and personal growth.