Natsumi-chan owns Hamtaro in the direct-to-video OVA "Tottoko Hamutaro Anime Dechu!". She attends an unnamed school and interacts daily with a classmate named Shinohara, meeting and talking with him after school. Her ownership of Hamtaro forms the central human-hamster relationship in this story.

Hamtaro once nibbled on her notebook, sparking her anger. She owns a dog named Wanta, a sheepdog sporting white fur and blue-gray ears. Before leaving for school each day, she expresses affection toward Hamtaro, telling him she likes him. However, she remains unaware that Hamtaro harbors romantic feelings toward her; she cannot understand his speech and views him solely as a pet companion.

Her interactions with Shinohara spark jealousy in Hamtaro, who perceives the boy as a romantic rival for her affection. This dynamic surfaces when she walks to school with Shinohara, prompting Hamtaro to spend the day venting his frustrations to Wanta. Upon returning home from school, she reassures Hamtaro by telling him she loves him very much, bringing him happiness. Her daily routine and expressions of care toward Hamtaro consistently frame their relationship.