You know how in a lot of anime the main character is a boy somewhere around 12 to 15 years old, just hitting puberty. He's got a good heart but he's kind of a loser. He's socially clumsy. He gets bullied and he never really fights back but somehow, he always comes through in the clutch. That's how our hero is in this series in the first episode, except that he is 17. What follows is not a spoiler because it all happens in the first episode. By the way, the anime starts somewhere around the third chapter of the manga. The anime just sort of starts in the middle. There is no real explanation of what is going on other than a few hints. It's a fairly obvious plot. You've seen it plenty of times. A high school class is suddenly sucked into another world where they must fight monsters and demons. You don't really see that happen. It is sort of alluded to in flashes. The story really starts when the boy-hero falls into an abyss. There he manages to survive long enough to eat some monster meat. This gives him more powers. He then uses his newly acquired powers to kill more monsters and acquire more powers. In the meantime, he comes to believe that the world has always had it in for him and his only course of action is to become ruthless and to take what he wants without compunction. He becomes single-minded in his desire to win at any cost, and yet there remains a deeply buried sense of good. It's very unusual for an anime boy-hero to be this decisive and to put his decisions into action without hesitation, even if those actions contravene accepted norms of social behavior. The title word means mundane, ordinary. That's what the boy-hero is at the beginning but he certainly doesn't stay that way long.
