The character known as Mei-san, often simply called Mei, is a neighbor in the apartment building where the main characters live. She is an elderly woman whose residence is located next door to Saku Fukuzawa and her giant cat, Yukichi. Mei-san is portrayed as a kind-hearted individual who is well-integrated into the community and maintains a friendly rapport with those around her.

One of her most notable traits is her calm and unbothered nature. Like the young girl Yume, Mei-san is fully aware that Yukichi is not an ordinary house cat but a colossal, bear-sized feline who walks upright and performs household chores. Far from being frightened or surprised by his extraordinary size and behavior, she accepts it without any apparent concern. This easygoing acceptance allows her to interact with Yukichi as a helpful neighbor rather than as a curious anomaly.

Her role in the story is that of a supportive and friendly neighbor. She and Yukichi share a positive relationship and are on good terms, often looking out for one another. This mutual aid extends beyond simple greetings, as they have been known to work together on community activities, such as volunteering to clean the local park. Through these interactions, Mei-san contributes to the sense of community that surrounds the main characters, providing a link to the wider neighborhood beyond Saku’s apartment and workplace. She is an observant presence who, along with other locals, becomes involved in the everyday misadventures and heartwarming moments that arise from the unusual living situation next door.