Shuumatsu no Koe

Rei Ametani lives his life day by day waiting for the sweet embrace of a merciful death. Although a former childhood trumpet genius, he now sleeps through classes—a much more ordinary lifestyle than his former one. This peace is suddenly interrupted, though, by a note found in his shoe locker. Believing it to be a fake love confession, he humors the sender by showing up at the appointed meeting spot. To his surprise, Sora Kamizono shows up with an unusual plea: she needs his help to destroy the world.

Kamizono is the first of seven angels from the Book of Revelations who has been sent down to Earth by God to sound the trumpets that will bring ruin to the world. The only issue is that she has no idea how to play the instrument. And so, Kamizono needs Ametani to teach her before the week is over. Eager to bring about a swift end to his life, Ametani agrees to help Kamizono during the remaining seven days. However, Ametani's and Kamizono's pasts flow to the surface, causing their resolve to waiver.