I had always just figured that TYL!Tsuna had somewhat anticipated his own death and prepared accordingly (either that, or they just had a coffin made short notice because there's no way Gokudera for example would have been able to move forward at all until his boss was at least temporarily laid to rest). There were any number of reasons why he might have resigned himself to the possibility that he'd end up getting killed in this timeline (especially since he had the backup plan of bringing his younger self to the future to fight in his stead); he did have that Vongola intuition backing him up, after all. And I also hadn't thought much about the timeline of the whole thing; I figured he'd probably been dead for a few days before TYB!Tsuna got there, and either they had some future technology! way of keeping his body from decomposing too quickly, or else it was manga logic and something Amano just hadn't paid much attention to. So nothing about the overall situation stuck out as overly suspicious to me. XD

I can't wait to see what Uni does in the next chapter. They still haven't explained how Byakuran convinced her to join the Millefiore (that's one thing his power doesn't explain--at least, not without us knowing all the details), so it should be really interesting. :D