That is a really great question. Minato must have known something we all don't, I mean he sealed the Kyuubi into his son and KNEW it would render Naruto as an outcast who would grow up in a life of solitude but did it to combat Tobi. Like I wrote I think Tsunade knows something and that something is not only speed being able to counter IWR/Edo-Tensei/Tobi's S/T Ninjutsu but so does Dead Demon Consuming Seal which I am sure she know's since FTG was passed down (as was the DDCS to Sarutobi and probably Tsunade as well). Then again back to your point, they must know a way to bring back the yin half of the Kyuubi or maybe they do not need it. Very, very good point I never thought of that and I haven't seen anyone point that out yet. One thing I also always wondered and Chapelle I would like to get your input on this, why do you think the Allied Shinobi Force hasn't used Edo-Tensei themselves, I mean it was created by Tobirama who was a Hokage and a good guy and I know it was a kinjutsu and blasphemous but still I would feel that every rule/moral is out the window as long as the world is saved.