So many characters in this series are so stupid. They are like small children utterly incapable of abstract thinking. They can only comprehend what's right in front of their eyes, yet cannot understand that what they are seeing could be something else than the first impression. Just like small children. Like if you show a small child a typical sleight of hand trick making a coin disappear, the kid will be all "Wow! Was that magic?", but a teenager, at the very latest, might be mildly impressed by your skills but would understand it was just a trick. In this series, however, most characters would react like the little kid, regardless of their age. Even more idiotic is that the MC summoned the demon king to help with the case, yet he wouldn't listen to a word the demon king says. Why the hell did he then even summon the man, huh? No wonder his school grades are dropping. He's an imbecile.
I wonder if the author is okay when this is the kind of stuff she writes.