Hiro lives next door to Kouji, having moved there two years before the depicted events. Kouji claims they are childhood friends, though Hiro disputes this due to the relatively short time. Physically, Hiro has long green hair and an average-sized body.

Initially resistant to Kouji's sexual advances, Hiro reacts with embarrassment and retaliatory urges. This resistance shifts to acceptance as Hiro consents to a sexual relationship, adopting a submissive role that aligns with Kouji's dominance. Hiro's submission partly stems from masochistic tendencies, finding enjoyment in the power imbalance.

Their encounters intensify from private settings to exhibitionism near apartment windows. They engage in oral sex, vaginal penetration, and masturbation. This escalation culminates in Hiro participating in a gangbang with multiple partners.

Later, Hiro's friend Rin discovers their activities and joins them in a threesome at their school. Hiro transitions from reluctance to active engagement in increasingly adventurous sexual scenarios, reflecting deeper exploration of submissive and masochistic preferences.