Tanpopo, a human from Earth, initially feels uneasy about her parents expecting a baby, uncertain about becoming an older sibling. Her life shifts when a malfunctioning device by Mametchi accidentally teleports her to Tamagotchi Planet. She sports chestnut curled pigtails with a yellow star clip, green eyes, a pink jacket over a red crop singlet, and a jean pleated skirt.

Thrilled to encounter real Tamagotchi characters as a longtime fan, Tanpopo aids Mametchi in confronting his fear of darkness, offering both emotional support and practical strategies. Her courage emerges during a critical space mission to retrieve Sunnytchi and stabilize the planet; she risks herself to save Mametchi from Blackholetchi.

Observing Mametchi’s bond with his younger sibling ChaMametchi—including their conflicts during the mission—Tanpopo gains insight into sibling dynamics. She mediates one such clash, reconciling the brothers while reflecting on her own impending role. After helping resolve the planetary crisis, she returns to Earth using a specialized key, now free of anxiety about her family’s new addition. Months later, she corresponds with the Tamagotchi characters via a toy device, expressing love for her baby brother and inviting them to meet him. The narrative closes with Tanpopo interacting warmly with her infant brother in a post-credits scene.