Kyōkai-sen [isekai]

(Creator's note: Kyōkai-se, or "The Frontiers" in English, is an RPG I created. Here's a bit of the story, or rather, the context.) Origins: A world where peace once reigned, where people lived in tranquility, until a strange red flash appeared in the sky and creatures emerged from it, plunging the world into darkness in the first era of chaos. In the second era, peace had more or less been established between monsters and humans. But you can create your own story, being the Hero or the villain; you choose your own path. So begin this adventure... (P.S.: It's an isekai, but not one of those isekai where the protagonist ends up meeting overly familiar versions of monsters, well, you know, right? But you can still do whatever you want with it.)