"Any card—so long as it exists—has a power that is needed."

houseofcardgames:

Can we talk about the fact that when The Fool spread darkness to one of Judai’s cards in season 4, the specific card it infected was polymerization

This is the same exact card that held all of Judai’s trauma from when he was possessed by the supreme king’s power in season 3– to the point where he had to stop using it because the memories it brought on was making him physically sick. When he finally used it against Johan!Yubel, he had to fight off being physically sick from the trauma it unlocked.

When season 4 rolls around we learn that the adversary Darkness is essentially the negative emotions, the anxiety depression and all of that that people carry with them, and that it can infect duelists’ cards if they associate them with negative emotions. Judai’s deck is fine at first because he has a strong bond with his deck and the spirits, as well as protection via Yubel’s soul fused with his own, but when Saio snuck the darkness infected Fool into his deck the one card that it affected was the one card that was shown to carry his past trauma. And once again, it ends up making him physically sick to carry with him to the point of nearly collapsing.

This probably seems very obvious, but this means that Judai’s darkness is 100% the fear of losing himself again. And if you ask me, it hints at the possibility that he very well could lose control of the gentle darkness power he holds and become the supreme king again. In fact it may be Yubel themself that prevents this, as at the start of the final duel against true Darkness, Judai’s eyes(full of rage and hatred no doubt) turn the supreme king’s golden color before Yubel’s multi chromatic eye color.

I had a final point but I lost it but I’ll just leave off with this being one of the reasons why Judai is and will always be my favorite yugioh protagonist. His character development is just. Some of the most extensive I’ve seen in the franchise so far, and is actually very relatable to me.