That seems the premise, kind of weird and somehow original, since it's always about saving the world. I'm not sure yet what does "destroy the world" mean, but it seems to be just that. Contrasting to the aparently dark theme, the manga is quite comedish, and seems to be alike to some other shounen with a tragic past hero. But well, I'm saying this after just reading two chapters (prologue and chapter 1), so there is still room for development.

After having watched the first two episodes, the best thing I have to say is that it makes me curious. There are enough, rather large, clues dropped to show the main characters have some sort of tragic or sorrowful past, which is one reason I'm curious. The other is that for all the seriousness of the plot, the actual goings on are rather goofy in their nature as many of the beastmen are in their appearence, rather unexpected voices and strange actions. These things combined with the rather dramatic (though also somewhat goofy) scenes shown in the opening, make me wonder if the goofing around will lessen in the future and fade to meer comic relief from a darker or at least more serious line.
Everything else aside, there were several times that the animators seemed to have given up on making movements look anything close to natural and actually reminded me more of bad acting in a cheap movie more then just bad animation.
All in all I don't think I will give up on it yet.