|Affiliation|| Unnamed Middle School|
|Parents|| Unnamed Father|
Saki Hanajima (Mother)
|Extended Family|| Megumi Hanajima (Uncle)|
Unnamed Great-Grandfather 
|Manga||Another Chapter 7|
Rio is a teenage boy of average build with a rather tall stature. Overall, Rio takes after his mother's appearance, including her facial features. He has short, black hair with long bangs framing mostly the left side of his face, as well as two cow-licks sticking out from the top of his head. Although it's not noticeable at first glance, Rio has an undercut. His hair is a lighter shade than his mother's, which may come from his foreign father. He has a pair of droopy, purple eyes.
Rio is a friendly, laid-back and level-headed boy who is understanding of the feelings of those around him, but also smiles very gently at all times.
Rio Mosca is the only child born to Saki Hanajima and her foreign husband. Because his mother is good friends with Tohru Honda and the other Sohmas, Rio ultimately became close to their children and grew up alongside them. Rio is also close to his uncle, Megumi.
Rio is good friends with Shiki and is always looking out for him. Despite being in different grades, they share common interests and are in the same club. They get along very well despite their different personalities, and Rio states that whatever friend Shiki has, that is Rio's friend too. It can be presumed that since their mothers became close over the years, Rio and Shiki did too.
Rio and Chizuru are good friends as well. He cares about him and his well-being very much, evidenced by the fact that he checked up on Chizuru when he was single-handely taking care of his father's shop, even when Chizuru had asked him not to. They are in the same club at school but different grades, but despite that, they get along well and spend much time outside of school as well.
- According to his uncle, Megumi, Rio did not inherit his mother's mysterious psychic abilities, so it is therefore presumed that Rio is a normal child.