If time could flow backward, and someone had another chance to save the world, then no matter the cost, it wouldn't matter anymore, right?
Even if the price were another world, everyone seems fine with that.
Everyone is doing what they believe is right: saving the world, whether by destroying their own world to save another, or destroying the other world to save their own. And so begins the farce of a group of people destroying worlds in order to save them.
And what about our protagonist, who's wearing a dress and is even cuter than a girl?
"Either save everyone or kill them all. No regrets, okay~"
