It's early summer, and Makino Yuu and Kunoki Nozomi have just officially become a couple. Walking to school together, sharing her homemade lunches, going on after-school dates — every small exchange slowly deepens their connection. Then summer vacation arrives with a full course of youthful memories: nervous excitement at the beach, fireworks at a festival, and the awkward thrill of sharing a room on a trip. Their friends — a cool, dry-witted beauty and a chaotic mood-maker — join them, bringing laughter, friction, and a lot of warmth. Just one summer. But for the two of them, an irreplaceable season.