Interesting concept. I'm wondering where you are going to go with it. I look forward to reading more.

I'm so happy you wrote another chapter, here's to hoping for more in the future. Patiently awaiting the next chapter ️

I can't believe how good your English is and how well you narrate this story! This is such good quality writing, I'm surprised it doesn't have any reviews yet. The thing I'm wondering about the most is whether this story will be canon-compliant, or different from the show. Either way, though, the premise and presentation are really interesting. Zuko's interactions with the old and new Water Tribe friends were sweet and humorous, while Unalaq and Zaheer's conversation was perfectly on-edge.

As a whole, this is really well done; but there are some minor details that could be improved. I'll try to organize them as two lists.

Regarding the story:
~ The ice bubble seems more attention-grabbing than just whispering news.
~ No one seems to actually inform Zuko of the new Avatar's name.
~ The way Senna and Tonraq say "the hell" seems a little out-of-character, or maybe it seems out of place for me since the rest of the conversation is pretty polite.
~ If this is meant to be the same as the show, you might want to look at screenshots of their house, because what you describe seems bigger (I don't think they have a dining room or a table, since they have been shown eating in the main room; and it doesn't seem like they have many guest rooms as you imply).
~ Zuko would still be the Fire Lord at this point; he retires three years before "The Legend of Korra" begins, when Korra is 13.
~ Since Tonraq is the son of the previous Northern Water Tribe chief, I suspect he may have met Zuko before his banishment; if they did not know each other personally, I think Zuko would have at least known of Tonraq.
~ I think Toph is famous enough that Tonraq would know who she is, and if he is friends with Katara and Sokka then they probably would have mentioned her already.
~ Korra's statement "Mommy's stories are boring" seems out of place. I don't see what it has to do with her not being sleepy.
~ If Zaheer had just arrived, he probably would have been prevented from disturbing Unalaq
~ It is unclear what kind of room Unalaq is in; I was surprised that there was a fresh pot of tea there. Was he expecting Zaheer to arrive while he was meditating? Would Zaheer not have to pass by guards or other people that might warn him that Unalaq was meditating?

Regarding grammar, spelling, and word choice:
~ There are a couple moments when it is unclear who is speaking, and it is not made clear until the following line or paragraph. This also happens a couple times when a pronoun is used, like saying "he" instead of Zuko, even after another male has been mentioned.
~ The names of the nations (such as Earth Kingdom and Water Tribe) should be capitalized, and names like "Fire Lord" and "Water Tribe(s)" are two words, not one.
~ I think "examined them closer" should be "examined them more closely".
~ "left to loose" should be "left to lose".
~ I think "gentler" should be "more gently".
~ The word "physically" doesn't seem necessary (actually might not make sense) before "restrain".
~ I think "mostly curious" should be "most curious" or simply "curious".
~ You slipped into present tense for "The Firelord eyes it critically".
~ "company has arrived" should be "company arrived".
~ I think Tonraq would speak more formally than "cause that's how it is"; maybe "because that's how she is".
~ I don't think "possibility" is the right word when Zuko is thinking about the new Avatar, because he knew all along that there must be one; maybe "fact"?
~ "as if he was" should be "as if he were".
~ I'm not sure what you meant by "waddling clothes"; according to my dictionary, those are strips of cloth used to wrap up newborn babies. A four-year-old definitely wouldn't wear them!

Sorry if that seems like a lot! I point them out because this story seems to have a lot of potential. I look forward to reading updates. Blessings on your writing!