Each year, mysterious cherry blossoms bloom across the crescent-shaped island known as Hatsune. It is on this island that Kazami Academy student Asakura Junnichi lives with a peculiar gift: he can see the dreams of other people while he sleeps. Additionally, an old woman once taught him a kind of magic that allows him to conjure sweets.
One day, Junnichi drifts into yet another dream, and inside it, he encounters a girl who was his childhood friend. But his sister, Asakura Nemu, wakes him up, dragging him back to his ordinary routine. Though Nemu shares no blood tie with Junnichi, the connection between them runs deeper than that of any real siblings—so deep that it resembles the bond of lovers.
Another peaceful daily morning begins: waking up early, heading to Kazami Academy, and hanging out with childhood friend Amakase Miharu, the school idol Shirakawa Kotori, and the two sisters Mizukoshi Moe and Mako, who love eating nabe on the rooftop at lunchtime. Just as their day settles into normal rhythm, a surprise shakes everything: Yoshino Sakura, their childhood friend who everyone believed had moved to America, suddenly appears in front of them. The moment she utters a phrase that catches both Junnichi and Nemu by surprise: "I've come here to fulfill the promise we made when we were kids."