I was thinking about the different types of jutsu that there are and the types that Naruto knows, and then how this relates to ?that jutsu?. It should be obvious to everyone that there are a wide variety of types of jutsu in the Narutoverse. These include: clone, prison, stealth etc. Now Naruto preskip knew the Kage Bunshin (clone), the Frog Summon (summon) and the Rasengan (short range finisher). He had obvious gaps in the other areas. Postskip the only new jutsu we have seen from him is the Oodama Rasengan, which is again a short-range finishing technique. The OR seems to be designed to do internal damage while the ordinary Rasengan does external. Now since Naruto has these two techniques as his short-range finishers, it is highly unlikely that ?that jutsu? belongs to the same category. What I propose to do is to try and narrow down the possibilities of what ?that jutsu? could be by looking at the different types of jutsus Naruto can or has learned. I?m also going to explain why I don?t believe that the common theory of it being related to the Kyuubi is right. To begin, I believe that Naruto created the jutsu himself. During the timeskip we were shown the Kakashi Gaiden where Kakashi unveiled his Chidori for the first time and was admonished by the Fourth because it was incomplete. He warned Kakashi not to use it again. I believe that this is a similar situation. Also the look on Naruto?s face when he talked to Jiraiya definitely made it look like it was something he was proud of. The other possibility for why Naruto was told not to use it is that it is too dangerous ? either to himself or to others. That of course ties in with the notion of it being incomplete. However Naruto is unlikely to need to be reminded not to use a jutsu which is dangerous to his comrades. Why it isn?t a Kyuubi Jutsu Essentially there are three reasons why I don?t think it?s a Kyuubi Jutsu (henceforth shortened to Bijutsu) 1)Naruto already has several Bijutsu. These include his regenerative abilities, the chakra roar, the chakra armour and of course the Kyuubi chakra itself. All of these powers have come naturally to him, suggesting that Bijutsu don?t need to be learned or developed. 2)Jiraiya warned Naruto not to use it. If the Bijutsu in question had any chance of releasing the Kyuubi, as many believe, then Naruto would not need to be reminded not to use it. In fact Naruto likely would never have developed it, and neither would Jiraiya have helped him learn it. 3)Frankly, it?s lame. It makes Naruto look like the only good thing about him is the Kyuubi and not his own powers and abilities. This jutsu is certain to be powerful and useful, though either dangerous or incomplete, and if Naruto was the one who created it then it reinforces the new image of him as a skilled ninja in his own right. If Naruto?s new trump card is just the same as his old one then nothing has changed. I?m now going to go over types of jutsus. Offensive Jutsus One of the most common jutsu types shown. These range from fireballs to sword techniques to crushing people with sand and so on. The only direct offensive technique Naruto knew preskip was the Rasengan. He also made use of standard ninja weaponry, Kage Bunshin manoeuvres and chakra-based strength. Postskip he presumably knows more, but the only one we have seen is the Oodama Rasengan, which falls into the same category as the Rasengan as a short-range finishing attack. These are techniques designed to finish off an opponent in one hit. Other examples are the Chidori and the Tsukiyomi. We can therefore logically assume that the new jutsu is neither one to enhance his strength or another finishing move, because it would be redundant. So what other forms of offensive jutsus are there? We have Tai rather than Nin, but Naruto is unlikely to have created a Taijutsu since he is much more talented in the area of Nin. Taijutsus obviously tend to be short range as well, so these would most likely be redundant. Now there are ranged jutsus such as Katons and other elemental attacks. These are a strong possibility because at present Naruto has not demonstrated long-range capabilities, so this would fill a necessary gap in his skills. Of course Naruto will likely have learned some elemental long-range attacks during the skip, but this would be a special one rather than basic. The only true ranged attack Naruto had preskip was his Bijutsu chakra claw, which worked at a medium distance but required entering Kyuubi mode. Offensive moves are flashier and therefore more likely by narrative laws to be ?that jutsu?. Also since Naruto will undoubtedly end up using it as a trump card it would make sense if ?that jutsu? were one. But it would have to be ranged rather than something like the Rasengan. Clone Jutsus Obviously these are techniques like the Kage Bunshin, Mizu Bunshin etc. Also obvious is that Naruto is a master of the KB already, which makes ?that jutsu? being a clone technique simultaneously more and less likely. On one hand, Naruto already has the KB and thus doesn?t need another technique that does the same thing. But OTOH, this means that if Naruto created an improved form of the KB that his combat style wouldn?t have to change to incorporate it. Also since Naruto is a master of the KB he would be more likely to know it well enough to improve it. Prison Jutsus These are jutsus such as the water prison, the toad stomach move used by Jiraiya, the ice mirrors etc. The closest Naruto has to a prison jutsu so far is using the chakra claw to hold on to someone. This is really only a prison jutsu if you push the definition. Naruto is lacking something in this area. However, if he has learned one it is most likely to be the same as Jiraiya?s, and so he wouldn?t have needed to create his own. The exception to that would be that we know Itachi is quite possibly the only one capable of escaping the toad stomach, so since Naruto was training to have to fight Itachi at some point then he might have needed to create something that could hold him. However this is unlikely. Something else that could be considered a prison tech would be the swamp technique Jiraiya used, and Naruto has probably learned that. Defensive Jutsus The only things which Naruto knew preskip which could be called defensive jutsus were both Bijutsus ? regeneration and the chakra roar. It?s therefore likely that Naruto has learned some that he can use at all times. Most likely he will have learned the spines of the underworld technique Jiraiya used which elongates his hair and turns it into sharp spines to hurt an attacker. Whether this is really suitable for Naruto considering the relative shortness of his hair compared to Jiraiya is another matter, so it?s possible that his new jutsu is defensive in nature. This could be revealed when whoever unleashes an incrediblky powerful attack that?s supposed to kill the heroes, only to learn that Naruto has used his super shield jutsu to save them all. This makes it a real possibility, since it would not be redundant and it could be dramatically revealed. Travel Jutsus These are jutsus that, obviously, allow you to travel from one point to another. Since Naruto is not a speed-type he will need some other way of getting around. Most likely he will learn the Hiraishin for obvious reasons. It is possible though that it is another form of travel jutsu. We have seen Kakashi and Kisame use moves to travel through the ground at high speed and Deidara and Gaara use techniques to allow them to fly. ?That jutsu? could be something to let Naruto fly or pass through matter and the Hiraishin would still be useful to him. Summon Jutsus These are not simple summons but specific summon techniques such as the Earth Tracking Fang used by Kakashi or Temari?s weasel wide-radius destructive tech. Summons with specific purposes, rather than simply summoning an animal. Now this could be ?that jutsu?, but it?s not going to be a frog summon technique if it is, since Jiraiya will have taught those to Naruto. It is possible that Naruto has signed a contract with another type of creature or created a bizarre form of summoning jutsu like the Edo Tensei or that gate summon. Seems unlikely however, since that would be overloading Naruto with summons. Seal Jutsus Now Jiraiya and the Fourth were both a master of sealing jutsus, as shown by how Jiraiya sealed up the Amaterasu and the Fourth sealed the Kyuubi. Orochimaru was capable of using the 5 Element Seal in combat on Naruto, and he is not as good as Jiraiya. If Jiraiya has taught Naruto sealing techniques then it?s possible that Naruto created his own. However the likelihood of Naruto being a master of seal jutsus to the extent of being able to create his own, incomplete or not, is low. Especially since he didn?t seem to know what the 5 part seal on the cave was. Stealth/Spying Jutsus I?ve grouped these two together because they?re diametrically opposed. Stealth jutsus are for hiding and spying jutsus for revealing. You could class the Henge, which Naruto is most skilled at, as a stealth jutsu since it allows one to transform your shape into almost anything. Other stealth jutsus are those to allow one to hide inside an element as the Demon Brothers did or ones to make you invisible like in the Gaiden. Now Naruto is possibly the least stealthy character in the series, so on the one hand a stealth jutsu seems unlikely? OTOH he is also the number one surprising ninja, and what better way to surprise someone than from coming out of nowhere? Spying jutsus Naruto was completely without preskip. He may now be able to use frogs to spy or possibly have other techniques, we don?t know. The likelihood of ?that jutsu? being one is low because it?s simply not flashy enough.