Hiiro should have invested in a good dagger. Imagine if instead of punches, he had delivered dagger stabs. The insect eye man would be pining for the fjords if not dead.
Hiiro actually has origin magic that he restores sliced rock back in one piece. Why he didn't use it and instead snapped after the books are burned, I have no idea.
@OllyMolly The soothsayer geezer taught him about the rebound effect, which has killed lots of strong magicians with unique magic. As long as he doesn't know what it exactly means and when it's triggered, it's pretty dangerous to use words like "die".