We know that when the Kyuubi attacked Konoha, the 4th Hokage sealed half of the Kyuubi's chakra using the Dead Demon Consuming Seal and half within Naruto.
When Orochimaru sliced the stomach of the Dead Demon Consuming Seal "Reaper"/Shinigami (Chapter 618), all things that was sealed in it was freed.
So what happened to the half of the Kyuubi's chakra that was sealed? Why didn't it return?