Board Thread:Versus Debates/@comment-43403813-20190805194702/@comment-9782468-20190808152148

Kaguya's aren't massively stronger (and if they were, it's not the actual reason they're so chakra taxing to open portals to), they're just massively further. Obito noted they were difficult to open portals to because they were so far apart.

Regardless, the fact that it's a different dimension makes it very taxing to summon to and from there. From Kaguya's dimension, 17 Kage were needed to complete a summon. Even if Nagato (as Pain) can summon Pains back from the Kamui dimension, the fact that it's a different dimension means it will be more taxing than summoning from their regular dimension. SO I doubt it can be used indefinitely, essentially.

However, have we ever noted a summon/reverse summon to work to/from Kamui? After all, when Obito sent Kakashi to Kamui's dimension and left him there, Kakashi didn't, for example, summon a dog to reverse summon out. We know that summoning jutsu take much less chakra then Kamui. So why did Kakashi use Kamui?

Also, during Obito vs Minato, Minato noted that if Obito touched him first it was over. Why would that be the case? FTG is basically a reverse summon jutsu, so if you could use summons to get out of Kamui then it would be useless against Minato. But Minato made a point of not allowing himself to be teleported away.

EDIT: in fact, why would Obito even think teleporting Minato was the way to beat him if he knew Minato used FTG? It's possible Obito's dimension is just one you can't summon out of or into