Chū is a small mouse stuffed animal and a close friend of the main character, Tom. He is characterized by a timid and easily frightened personality, often getting nervous and rushing into situations, which tends to cause trouble during their adventures. Despite his anxious nature, Chū sometimes speaks in an old-fashioned Edo-style dialect, using phrases such as 合点承知 (gaten shouchi, meaning "understood" with a historical flair). He has a fondness for playing the drum, which is his favorite instrument. Chū is almost always seen together with Tom, joining him in exploring the house and playing with Tomica toy cars when the humans are away. His role in the story is that of a loyal, if slightly accident-prone, companion whose impatience and fearfulness often lead to comedic mishaps. Over the series, he develops through his shared experiences with Tom, though his core personality remains that of a nervous but well-meaning friend. His notable traits include his distinctive way of speaking and his love of drumming.