So I assume "That Jutsu" Jaraiya was refering to was some kind of advanced jutsu related to the Rasengan. I dont think it is the Tailed Beast Bomb because Naruto would have mentioned that when he was training with Bee.
Watching the latest episodes his hands were scuffed up and he needed the 9 tails chakra to help perfect it. Plus it's a part of the 4th Hokage's Legacy which Jariaya said he could not understand but it seems the 4th either was able to master it or at least understand the mechanics behind it.
I think Jiraiya was using jutsu in a broader term
than you are taking it to mean.
I'm pretty sure what he meant by jutsu was
using the nine tails chakra without being
corrupted by it's will (it is after all what
the whole flashback was about, and Minato's
legacy to Naruto is absolutely the nine tails).
Jutsu after all refers to any and all
of a ninja's moves, not just ninjutsu like
you seem to be taking it to mean.
Zabuza said "the same jutsu won't work
on me twice" to Kakashi referring to the
sharingan. Kakashi's sharingan is always on
and falls more into the lines of native ability
than a move as such. The nine tails falls pretty
much into the same category for Naruto.
Punching someone in the face is a jutsu if you
do it the same way every time.
Basically the whole little flashback was a
testament to how Jiraiya failed at helping Naruto
master using the nine tails chakra. Then he gets
the prediction from the toad and goes on a mission
to master the nine tails chakra. Makes perfect
sense that way, you are just digging for something
more from it really.
@Almightywood: Just like you said Jutsu is a
broad term and can mean any kind of technique.
For all I know he could have just been trying to
show him how to control the nine tails chakra. In
case you didnt read my whole post I am asking for
any thoughts on what Jutsu Jaraiya is referring
to. I just dont happen to think it's the
tailed beast bomb or any of the training that
Naruto did with Bee (I may be wrong of course).
And yes I may be digging but a Jutsu is a
Jutsu whether its to control chakra or fighting
and I think Naruto would have mentioned that he
had similar training to Bee if that were the case.
So I am asking if anyone has Any thoughts on what
kind of Jutsu Jaraiya was trying to teach Naruto.
Thank you for yours.
Personally, if I had been taught how jet engines
work by a car mechanic, then went to train under a
jet engine specialist, I wouldn't be too
detailed, I'd just say something like:
"I understand the basics". I think this
is kind of the same scenario.
which, Naruto doesn't tend to talk about past
training unless it can be applied to current
training. When he was training to master sage
jutsu he didn't mention what training it was
that he sped up by using shadow clones, only that
he had done it. This led to the ma and pa sage
toads being surprised at his rasen-shuriken.
Flying thunder god technique seems
to be very far-fetched to me. It
shouldn't require the nine tails chakra as
minato didn't have access to such when he
used it. If Jiraiya was trying to teach him such a
technique, that he himself could not master, why
should he complicate it by bringing the extra
effort of fighting the nine tails will into it?
If it isn't the nine tails chakra
that he is referring to (highly doubtful imo), it
is assuredly some kind of kekkai genkai. It would
have to be to fit the phrases "minato's
legacy", and "only you can master
this". Flying thunder god technique
doesn't seem to be kekkai genkai, it is
simply one of the techniques he created.
@ Almightywood: Thanks, I never really thought of
a Blood Line Limit but that is definitely a
possibility. And it would make sense given the
context of Jaraiya's comments. The Flying
Thunder God Tech. is a good one but just like you
I don't think it was what he was referring
to (unless there are more levels that can be