Hiyoko debuts in the OVA as a new character. She collaborates with Hinako during bathing and stretching routines. Together, they guide viewers through practical bathing habits and after-bath stretches, demonstrating techniques. Hiyoko directly acknowledges the viewer, reinforcing the interactive nature of the content. Introduced partway through the OVA, her arrival shifts the focus to shared activities between the two characters for the remaining runtime. The OVA was distributed via microSD card bundled with physical releases for mobile viewing. No canonical background, character development, or expanded narrative roles exist for Hiyoko beyond this single appearance.