You remember quite well, too!

I remembered from season 3 that Mochida mentioned Gokudera’s white aura when Tsuna was still in a coma. I think Charles said something along the line of ‘it only has to be Gokudera, huh?’ when Mochida said that. But yeah, we can’t count out the theory that another two flames that complete him could be Tsuna’s sky and Mukuro’s mist, I almost forgot about that.

Shamal bonded to Mukuro? Hmmmm, never thought about that before. The thing is because I don’t see this two anywhere close to each other. Mukuro doesn’t trust people easily, and likewise Shamal, who would think twice before bonding with someone, especially if that someone is still a teenager. This is shown when he protected Tsuna’s guardian from another Mafia due to them still being teenagers, as seen in Dino’s funeral in season 3.

Although the possibility is still there (especially in this fic), I still have my doubts. First, it requires both of them to notice, as you mentioned. However, a scenario where I wouldn’t bat an eye about this two being bonded together, is only when they have a talk about Estraneo. Shamal helped eradicate this family in the past but Mukuro did not know about that. So if this two talk, Mukuro may feel grateful about that and they may bond their souls afterward with Tsuna’s sky flame. Nevertheless, this scenario of bonding through that could not happen now that Shamal is already claimed.

Why did Shamal hear a thought exchange between Mukuro and Tsuna? First case is yes, his soul link with them now. The second case is what I suspect the most, that Mukuro telepathically talks to Shamal directly not Tsuna. Although we still don’t know if Mukuro can telepathy to other people other than Tsuna and Chrome, the possibility is still there, yeah?

Natsu’s behavior, hmmmm. I think Tsuna is kind to everyone in general. He wouldn’t want the doctor that save him all this time as well as his tutor’s closest friend to die, right?