DB Multiverse

(In case it's not clear, it’s Gohan from universe 16 on this page. He talked to the Kaio Shins during the night, as was said several pages ago)

Hi everyone.

Sorry for the long text, but I wanted to explain a few things about potala-fusion.
Gokû's explanation regarding the de-fusion of Vegetto inside Buu never convinced me. The real reason is actually never told and we all understand it was merely a trick from Toriyama to separate Vegetto.
I’ve invented a reason, and this will be DBM-canon. Before carrying on, here is some more informations about what I invented about the Kaiô Shins.

Have you never wondered why those guys wear the incredibly powerful and dangerous Potalas around? It’s the treasure of the Kaio Shins, the old one said. And, of course, as East Kaio Shin was too young, he didn’t know about them.

So I've decided they were invented by and for the Kaio Shins. They would work only if one of the user was a Kaio Shin, and he would use it to gain abilities from another person. It’s not an equal fusion : the old Kaiô Shin used 'I' when he spoke of the younger Kaio Shin and 'she' when he spoke of the old witch. Same goes for Kibitoshin, he spoke of Kibito as another person. Contrary to the dance-fusion, the Potalas allows one Kaio Shin to “absorb” another being!
(Of course I’m only interpreting a few sentences, but I decided this to be official in DBM).

This means that someone who steals the Potalas won’t be able to use them.

This also means that old Kaiô Shin modified the Potalas he gave to Gokû. Of course, this isn’t told in the manga, and clearly he didn’t take the time to explain, but please bear with me here and accept that he did modify the potalas in a second because it was easy for him, and he didn’t talk about the details.
This whole theory could even work without this “Kaiô Shin only” rule, but it will help reducing the number of fused people around and also explain why it feels like the Kaiô Shin doesn’t treat the other fused person as an equal.
As Gokû isn’t a Kaiô Shin, an “upper” being, the resulting being considers Vegeta an equal, so it’s like a dance-fusion : a new being, not simply a better Kaiô Shin.

Remember that the Kaiô Shins are very arrogant, and don’t think much of the “lower” beings. Also keep in mind that the old Kaiô Shin enforces lots of rules, he is very strict about them (although he understand the whole universe is in danger and that’s why he agrees to create Vegetto and to use the Dragon Balls).

This takes us to the inside of Buu. It now fits perfectly.
Kaiô Shins' essences are in Buu. Vegetto is “illegally” using a Kaiô Shin device.
They act on it and “split” Vegetto.