well the most important thing he learned was "To never give up!" ... and also I agree with most that whatever 'that jutsu' is, it has to do with the kyuubi chakara. I also think that it may be something he learned in the scroll that he stole in the 1st chapter, written by Hashi, and married to the 1st kyuubi jin... im sure that she learned how to use and manipulate the 9t chakara to form new jutsu's, especially with Hashi being her husband, and being able to supress the demon if it wanted to break free..