Rei Ametani, once a prodigy in trumpet playing, now drifts through life yearning for an end. Routine is shattered when he discovers a note in his locker, leading him to Sora Kamizono. Unexpectedly, Kamizono, an angel tasked with world destruction, seeks Ametani's aid in mastering the trumpet. As days dwindle, their shared histories resurface, testing their commitment to the impending apocalypse.