ok check it out. i'm not sure who has yin and who has yang, but the power the Kyuubi regained was the power taken by naruto. everyone depletes their own chakra in battle, and they regain it with rest. whatever chakra naruto stole from the kyuubi, the kyuubi gained it back.
think of it like this--if Naruto took ALL the kyuubi's chakra, the kyuubi would have died. but after Naruto took the power, the Kyuubi threw another TBB at him. the kyuubi still had a little chakra to spare, and it's THAT chakra that regenerated