@Udin
You know what when he first came to new world Naofumi was like that too. Happy to be there, excited. If he got the same behaviour from that world im sure he would've been the good and just hero. He already is actually. Just knows the real faces of humans thats all.
Well, Naofumi is actually a good and just hero ( or atleast the best out of his world ). He is just not a happy or optimistic one, like Kizuna ( still ? ) is ... and not by his fault, remember :/
Hey hey! After the whole turtle arc, the pace has picked up and things are starting to get interesting again
Seeing how Naofumi comparing himself with Kizuna, with how, maybe, if things didn't go so bad at the beginning he could have a very different look on the world