Riiya, a wolfboy residing near the protagonist's home on Mochimochi Mountain, is her steadfast childhood best friend. Initially, he provides unwavering companionship and protection during their adventures, often positioning him as Shiine's rival for the protagonist's affection and creating a recurring love triangle complicated by his largely unexpressed feelings.

His protective nature emerges when he intervenes in Yakko's duel challenge against the protagonist at magic school. Riiya also displays vulnerability, nearly drowning and sustaining a head injury that causes temporary amnesia. Marin the mermaid rescues him, subsequently developing persistent romantic feelings for Riiya. Her advances and later transfer to their school create ongoing tension, especially after a love potion mishap causes classmates to fall for her, though Riiya's romantic focus remains elsewhere.

Episodes occasionally reference Riiya's family, such as when his grandfather visits school and consumes the entire lunch supply, causing a food shortage and highlighting their distinctive traits. Riiya faces recurring physical threats, including being kidnapped by the vampire Kyū-chan during a rescue attempt involving his friends.

In later developments, Riiya participates in acquiring magical artifacts like the Phoenix Sword, crucial for the protagonist's transformation. His role expands during confrontations with the primary antagonist Daimaou, where his connection to the protagonist proves instrumental. The OVAs maintain his established characteristics without significant additional development.

The manga source material diverges by omitting the magical princess storyline and Daimaou pursuit arc. Here, Riiya's involvement remains focused on comedic interactions within the core trio alongside Shiine.