When he was alive, he was drained of chakra. Why would he go to the afterlife with no chakra? If in the afterlife, he's a kid again, it's safe to assume he is also at peak performance, chakra and stamina wise. You don't see him out of breathing or breathing heavily, do you?So obito needed sakura's chakra for inter dimensional travel when he was alive but when he died, he can kamui to kaguya's by himself?