One more 6927 present era headcanon about them getting together:
Tsunayoshi initially thinks Mukuro is way more serious of a person than Mukuro actually is.
Like, while WE know hes the type to do things for shits and giggles due to his interactions with lets say the Kokuyo and Verde, Tsuna does Not. Hes still kinda operating on how Mukuro and Tsuna interact during literally every other arc, wherein Mukuro is trying to farm aura points.
So what happens is Tsuna goes into this relationship antsy af. He thinks hes about to date some cool guy who is also like, villainous. Is Tsuna Really up to this? Will Mukuro get bored of him? Will his first ever break up ruin dating for him forever? WAS THIS A GOOD IDEA?
Then Mukuro makes some fucked up joke/pun and Tsuna, the infamous "i gotta be the only serious one here and if not i will be making bad jokes about the entire situation" guy of the Daily Arc cant help it --- he snorts
Mukuros eyes light up a little at someone he kinda likes actually getting his bad and sometimes sadistic humor that isnt his apprentice. He doubles down on the joke/pun to the point its pure dark humor now. Tsuna cant help it again -- he makes a sarcastic remark back.
By the time anyone finds them they are both doubled over with stomach pain laughing because they both think they are funnier than they actually sre.











