Kaito, a boy with a deadly heart disease lives in a world of constant pain and struggle whos only goal is to confess to a cute girl he likes in hopes that it would make his life less hopeless.
However, he sufferers from a heart attack before he could, and finds himself in a limbo world where time doesn't move forward along with his crush who was actually a fallen angel all along.
He must now protect her from a true angel who wants to destroy her and he questions if all the pain and suffering he has to go through is worth it, or is it better to die and feel nothing at all.