Kei stumbles through his final year of high school carrying a secret that could destroy everything: he's not entirely human. Years ago, a mysterious incident left him in suspended animation, and he's awakened to find himself trapped in a body that won't age while the world has moved on. When Mizuho arrives as his new teacher, she recognizes something in him, a kindred spirit hiding her own extraordinary nature. What begins as an awkward teacher-student dynamic spirals into something neither of them expected. Mizuho's presence threatens to expose Kei's carefully constructed normalcy, yet she's the only person who truly understands what he's carrying. As feelings deepen and secrets press closer to the surface, they navigate the impossible space between duty and desire, between the lives they're supposed to live and the ones they actually want. This OVA distills the original series into a single, concentrated dose of romance and science fiction, capturing the central tension that defines their relationship: two people caught between worlds, finding solace in each other while the clock ticks down toward an inevitable reckoning.