
I believe that Suu found out and figured out quite a bit while carrying out Jin’s errand. Saharah revealed himself to be a dragon, which Suu had a difficult time accepting since he doesn’t even believe dragons truly exist. However, this was confirmed by Jin.
Suu realized that Jin is in fact the Crown Prince, which is why the royal consort found it so amusing, making up the story that the crown prince “favors” Jin. Suu confirmed his hunch though his and Jin’s ambiguous conversation, without directly asking.
Nevertheless, everything that Suu has recently learned is ultimately rendered null and void since his memory was wiped once again when Jin healed him.
...Although I question whether his memory was actually wiped this time, since he is building up an immunity to possibly both the poison and healing side effects. Jin also knows how well Suu is able to “play dumb”, since he admits that he used to frequently do the same.

Thanks for the input guys!! As the story goes on it gets more and more complex or should I say everything is getting more clear. I'm looking forward to the next chapter to see whether he did in fact lose his memory or is "playing dumb". Either way I might read over the last couple of chapters and see if I missed something.

It seems everyone's forgetting about what Suu was thinking before I assume they did it, or something happened anyway, and then he lost his memory. He's really hungry again.. his mouth feels sandy.. it seemed even that he was looking at Jin as a food source. Either Suu is slowly developing the symptoms of Mara, or he developes symptoms every time Sahara feeds off of him, and every time, Jin heals him.
So adult dragon dropped some hints of what is going on. Jin and he are connected. Whatever he is attracted to, so is Jin and vice-versa. He can't use Jin's blood because it's cursed so he needs an in-between. Somehow that is Suu.
Suu is being immunized against the dragon's venom and his body seems to becoming tolerant of it to the point that in the later chapters he doesn't faint or pass out at all. In fact, when he jumped out the window to escape the dragon he was able to recover from it without healers or Jin. He threw up and had a fever for days, but he was able to recover without dying.
Jin's servants comment that the dragon feeds on Suu but not the point of death. It drains him to his limit and then lets him recover. The dragon also says that not only does he intend to "become one" with Suu and put some of his power in him, he also intends to take him to a "higher place".
The dragon said "You eat Jin. I eat you". Apparently Suu is gaining energy from Jin's regenerative blood and the dragon then feeds from Suu. I guess Suu is like a water filter at the moment. He filters out the poison. Since he started making out with Jin he seems more resistant to the dragon's venom.
Jin seems increasingly obsessed with Suu even though he hides it a lot. He intends to keep Nadan as leverage over Suu. He even tells Suu that he'll pardon Nadan if Suu agrees to stay and take care of the dragon.
However, I don't think he really plans to let Suu free at all. He also is hella jealous of Suu's love for Nadan and seems to want to kill Nadan for that reason alone, but keeps him so as not to lose his leverage piece over Suu.
He also seemed rather angry to learn that Suu has been saving up to get him and Nadan out of Rahan. Suu wanted to cross the borders. It's clear Jin is more attached to Suu than what Jin can accept. He's not someone used to being that attached to someone. I think on one hand he wants to kill Suu and on the other he can't stand the thought of not having Suu where he can have him.