So we know that Kawaki is for sure the vessel, but we don’t know what the vessel is supposed to contain or if Kawaki is containing whatever it’s supposed to be already. If I had to guess, I’d say the vessel is supposed to contain an otsutsuki spirit of some sort if Kara is really connected to them and I’d say that Kawaki is currently an empty vessel and that Jigen is currently acting as the vessel. It’d explain why he looks like the leader, why he personally went to collect Kawaki and told Kawaki to call him father since it’s traditional for a father to pass on his possessions to their child.
This part of the theory I’m not entirely sure about because I’m not sure if Jigen has the karma seal or not, but if he does then I would think the karma seal would be needed to act as the vessel and that’s why the rest of Kara is so shook when they find out Boruto has the seal as well. Either that or Karma is the name of the seal that every Kara member has.
Tldr- Kawaki is gonna be the vessel for an otsutsuki that Jigen is currently holding and the karma seal is key to being an appropriate vessel or the name of every Kara members seal
This part of the theory I’m not entirely sure about because I’m not sure if Jigen has the karma seal or not, but if he does then I would think the karma seal would be needed to act as the vessel and that’s why the rest of Kara is so shook when they find out Boruto has the seal as well. Either that or Karma is the name of the seal that every Kara member has.
Tldr- Kawaki is gonna be the vessel for an otsutsuki that Jigen is currently holding and the karma seal is key to being an appropriate vessel or the name of every Kara members seal