Guillotine Bride, Vol. 1 (manga)

Rinne Irako, a girl with the potential to bring the world to ruin, has been sentenced to death. But on the way to the guillotine, a sudden incident sends her crashing down to earth—right in the path of Ryuunosuke Dazai, a boy who’s eager to help save Rinne and the world. All he has to do...is marry her?!