In a near-future society facing a sharp decline in male births, new legislation grants special privileges through the Free Sex Licence to help address the crisis. Takumi's routine changes overnight after he receives the document, leading to encounters with the inquisitive genius Sara and Misaki, the older sister of his childhood friend. Rin, who quietly cares for Takumi, grows increasingly unsettled by these developments. Tension peaks when the licence is inadvertently shown during class, resulting in a public moment that draws Rin directly into the situation.