Hamutaro's background involves early separation from his mother, Yuki, seen only in a baby photo within his owner Laura's album. Viewing this picture during a birthday reminiscence sparks an overwhelming urge to reunite with Yuki. He immediately sets out on the long journey to find her, demonstrating profound familial longing and spontaneous determination.

Friends Boss and Oxnard accompany him on the exhausting journey, measured as 3000 "ticky-ticky" steps. The trek demands persistence through deep fatigue. Hamster Jingle indirectly aids them by providing transportation via Herbert, though this causes unintended detours that complicate the quest. Hamutaro's resolve stays firm; he even seeks aerial help from Françoise to reach Sumire Town preschool, Yuki's last known location.

At the preschool, he meets Tsurara, a white-furred hamster resembling Yuki, whom he mistakes for his mother. Tsurara clarifies her identity and reveals Yuki is in a "far, far away place," implicitly indicating her passing. This marks a pivotal emotional shift from hopeful searching to confronting loss. Tsurara directs him to look skyward near a sunflower patch at sunset, where he sees Yuki's form in the clouds. Yuki communicates enduring presence, offering him solace and acceptance. This concludes his active search, replacing it with an understanding of spiritual connection.

He returns to the Ham-Ham Clubhouse for a deferred birthday celebration. Joy resurfaces during the festivities, especially through his friends' musical performances. The event culminates in a shared birthday acknowledgment for Cappy, extending the communal happiness. It closes with a silent tribute to Yuki, symbolized by flowers dropped under the night sky, integrating his loss into his ongoing life with the Ham-Hams.