|Relatives||Russel and Lori (owners)|
Winnie is an all-black puppy whose breed is likely that of Labrador Retriever. He has large brown eyes; a sleek, short coat; and wears a brown leather collar and leash.
While still in elementary school, Rin leaves Japan and goes to Sydney in order to attend a school with a powerhouse swimming team. While there, he stays with a family whose given names are Russell and Lori. Being concerned about the boy's adjustment to so many changes ane new customs, they obtain a puppy to cheer him up and to keep him company.
- An alternate spelling of the dog's name has been suggested as Winny. Either spelling is a pun on the English word, "win."
- Winnie, along with Lori and Russell's house, is said to be based on a real dog and house that the series' staff saw on their reference trip to Sydney for Free!-Eternal Summer-.