Such an awesome comic!! x3 Loved every single page of it. Oh, everyone's grown up! And the mystery! Gotta adore it x3
Now, as far as the letter Zuko's reading on the last page of 'The Search Part 1' is concerned, I don't know if that letter is EVEN true. Ursa was definitely a smart woman. Wouldn't she get suspicious by not receiving back letters from her homeland, where she'd always write to? Maybe she understood that, and wrote a fake letter to Ikem. As in, she knew the letter would eventually come to Ozai's hands and wanted to mislead him.
Now, I've kinda given it some thought. Maybe Ursa couldn't stand a life without Ikem, and she thought that if Ozai found that she had (hypothetically) cheated on him, and Zuko was an illegitimate child, the prince would ask from his father (FIRE LORD Azulon) her and Zuko's banishment. So, Ursa would go back to Ikem, and also manage to take Zuko with her; Zuko, a child not really favored by his father, in contrast to Azula, whom Ozai favored due her firebending skills. To sum it up, she could go back to her old life, taking Zuko with her- protecting him from his father's cruelty (which could also mess him up pretty badly), while Azula would definitely be safe.
Something else, it would be interesting if the bastard child was actually Azula! Azula bends blue fire, the same color as the wolf who chased our heroes during their trip to Ursa's homeland. Also, we see that the wolf visits Ikem (or, rather, meets) when he's alone by some lake. Plus, when Azula gets freed from the ice Katara had trapped her in, she just flashes some lightning and the spirits go away. And how did she EVEN know how to make them go away (she confidently tells Zuko that she could help them)?! Maybe Azula has got some connection with that wolf spirit. Let's not forget that, when the wolf-spirit first shows up, it's not angry, but when Azula gets tackled to the ground, it gets mad as hell.
Not to mention that Ozai married Ursa to complete the sages' prophecy. We know for a fact (from LOK) that Zuko ruled the Fire Nation for many years to come (realization of the sages' prophecy), while Azula had initially planned to overthrow him with the letter she'd found. This increases the chances of Azula being the illegitimate child even more!
UGHHH!!! I CAN'T WAIT FOR PART 2!! Y U SO FAR, JULY!?