Naruto, the main character of the popular Anime show "Naruto Shippuden" has several arsenals at his disposal. One of them is his huge amount of chakra given to him by the nine tailed beast, the demon fox, and another would be the huge amount of healing power it gives him.
In episode 156 of Naruto Shippuden. It has been revealed that the Sage Mode, a whole new category of Jutsu that seems to surpass ninjutsu, accelerates further Naruto's healing ability. As shown in the episode, Naruto hears this fact and generates an idea in his mind which he later on practiced without Lord Fukasaku's knowledge.
Even though obvious details that would give away the nature of the Jutsu have been purposely hidden, there are several clues we could expand on. The first one is that it was a Jutsu, mentioned in earlier episodes, given to Naruto by Itachi Uchiha with implications that it could be used to defeat Sasuke Uchiha. The second is that there was a gigantic plume of smoke about Naruto after he was shown using it.
The first clue leads us to the fact that during Itachi and Sasuke's fight one of the techniques that Sasuke Uchiha could not counter was Itachi's last move, Susanoo. That being said, it is climatically logical for this particular technique be the one Itachi Uchiha has relayed unto Naruto. The huge cloud of smoke dispersed about Naruto after the technique ties in with the humongous size of the summoned creature when Susanoo is performed.
