Main Character Hides His Strength. He was playing a game with the a demon that was locked up in the castle.
I think it's not even past chapter 50, why don't you try searching for yourself first. And sorry I have't read this MCHHS so I can't help you.
That's what I thought, but I'm rereading everything and can't remember past chapter 5... I remember reaching chapter 40 though which is weird... edit: I read this at night and hadn't slept the day before, so my mind was foggy... Lol, guess I have to reread everything.