Wait is he even isekai'd from Earth? I skimmed over the previous chapters and he just popped into the new body but never gave an age or how he died.
I was planning to give him shit not knowing what prime numbers are (can excuse not being able to list em) but he might genuinely not know.
@Akxera
I think the dude was basically saying, "You don't have enough magic power to handle a certain number of spells at once for a long period of time. But as you get stronger that limit disappears. And so here is a McGuffin meant solely to focus you on the task of getting stronger instead of getting depressed when you hit a wall in your training."
@lioslin it isn't clear, the weird item box spell he uses in the first chapter, along with the massive rock it carries, usually seems to be tied to "real world" huemans. Maybe the second time he got isekai'd made him forget most if not all of his original identity.
Or maybe he just got isekai'd once from another fantasy world.
This manga is interesting I like it. Thanks for the update, please continue translating this manga really love it. Thank you translators can't wait for the next update.