I refuse to level up! (Don’t ask about my sister’s opinion on this)

What would any normal person do after they isekai'ed to another world? Well that shouldn't even be a question. Grind up levels, become strong and conquer the world with overpowered cheat abilities. But Ren isn't that kind of "Normal" What if he conquers the world without levelling up? without becoming strong? without a single cheat skill? For a diehard Batman fan — that was never going to be a problem. Right?