How do summoning jutsus work?

Question

Let's have a back drop on the story, the Third Hokage shows Jiraya, Tsunade, and Orochimaru his summoning technique. This intrigues Jiraya and he too tries to perform the jutsu without making a blood seal with an animal. As a result he is teleported to Mount Myoboku, where the Toads live. He trains there for some time.

Here lies my first question, until later into his training Jiraya had not made a blood seal with the toads, so how did he get to mount Myoboku to undergo his trainings? The reverse kuchiyose should only work when there is a blood seal with the animal. Going to Mount Myoboku on foot is a long and tiresome journey, so this possibility too is cancelled out. So, in order to go to Mound Myoboku did he use the kuchiyose no jutsu every time?

My other question is what decides which animal a shinobi is to bond with? There is a wide range of creatures that one can choose from, but certainly there must be some sort of compatibility to be worried about. What made Jiraya decide a toad summon would be best for Naruto?

Has anything that can substantiate the above points been mentioned in the manga?

Answer 1

Nope, it isn't explained at all.

The background you described is 100% filler and was never described in the manga, so using the Summoning Jutsu without a blood pact doesn't necessarily teleport you randomly.

As for which animal is suitable for which. Jiraiya seemingly decided to give Naruto the frog contract because he had the contract himself, (not to mention that Naruto's father, Minato, also had a blood contract with frogs).

I don't think there's a requirement of any sort, but that's just guessing. The entire technique is cloaked in mystery.

See my answer on this other question: How to summon a different animal using Kuchiyose?

Answer 2

The summoning jutsu is similar to time-space ninjutsu in that it connects two dimensions together for instant travel. For this to happen one must make a blood contract with a summons. How this takes place is unknown and unexplained, but it was stated that jariya found the hidden entrance to mount Myoboku and trained there. It can be assumed that after his training he acquired a contract with the toads. He then made a contract for minato and later naruto. Other people may have been able to make contracts like this as well as orochimaru was seen finding the entrance to the cave of the snakes. How tsunade made a contract with the slugs is unknown (and wether there is more than one slug).

On the question of compatibility there does seem to be conscious decision when picking a summons, however it does not inhibit a signing of a contract. Jariya happened to have fire which worked well with the toads oil and naruto happened to develope wind nature which happened to work well with the toads water but this was found out some 2.5 years later after he signed the contract. And minato seemingly had no natures yet he still has a contract. I would say that it strongly influences a decision to make a contract seal but does not dictate a sealing.

And on the basis of jariya's movements between mount Myoboku and the real world it can be assumed that he made a contract upon his first stumbling upon the mountain, and from the on used the reverse summoning to go back for his training over the years.

Answer 3

Just like how every shinobi has a unique nature for Ninjutsu. All shinobi have unique summonings.

Not ALL summonings need contracts, in Sasukes and Madaras case they can summon animals without contracts. Sasuke simply placed his hawk under genjutsu and bound the hawk to servitude probably after finding it in an unknown location. Jugo probably lead him to it.

Madara found the Nine Tails during his journey around the 5 Great Nations. And put it under a simple genjutsu bounding it to a contract for summoning.

Maybe sasukes summoning isnt genjutsu bound but his summoning can't talk AT ALL. Only kishi could explain.