At first it was understandable. But the moment he defeated the sea dragon (with help) and everyone was so amazed and he was told about barely anyone ever defeated one he should have realized. And even more so after the explanation he got for advanced classes, and how they're considered inferior because none of the skills/spells seem to go with them for the people of that world.
Being oblivious is only believable to a certain point...
ikr the beginning was fine but like he has been explained to multiple times about his strenght and he still doesnt even bat an eye at the fact that if he really was weak like he believes to be he would never have been able to defeat an a rank monster while still at f rank at the guild. even the critical strikes that he keeps pulling off which had like a 20 % chance from the strongest person in this world... i somewhat have a bad feeling that he is probably going to realize this very late into the story if ever...
i kinda dont really like how oblivious he is to his strenght.. like i mean yeah i get why he is like thta but he even said in the beginning that this is different to the game and how behind this world is to it but still continues to use the games standards as his common sense without even trying to actually figure it out.. but i still like the story so far tho