Yume-chan is the technical owner of Maxwell. He is owned by her older brother, but she's the one that actually looks after him. She is also the youngest child of the library owners.
In the episode A Little Love Story, She writes a book about a Hamster called Nana and her love for a hamster named Yu.
Trivia
- If she was dubbed into English, she would have been named Melissa (hence the title of Episode 139 would have been "Melissa, Tell Us a Story")