Why Naoya can not see his red string while Gojo can?
Well let just say for angst purpose but!
It's more of univers way of saying "fuck you" to Naoya since Naoya really a shitty person. Basicly make Naoya think he is unloveable. Which give Naoya a understanding that IS true for him because he pretty much aware of people disliking for many reaaon. So even he aware of that he double down with his personality since he dont know what else to do. Naoya crave genuent relationship, rather friendship or love life but the reminder of him being unloveable make him sabotaj himself in any chance of the relationship he ever get since in his head all he think about it. "You'll will hate me one day too"
But even the univers did that, they not cruel. They have their own twisted way of how someone like Naoya could be love. Just not in right time yet. That's about love hmm, all it take is right time.
They get togather. They soulmate for a reason and no one could run from fate. Not even Gojo Satoru. Fate in mystery . No one actually know how it work. That leave us wondering. The piece of fate that they get already put them in chaos. But it is what it is