In Naruto, Kurama (the Nine-tailed bijuu) appears as chakra, as does Killer B's bijuu, Gyuki.
Other bijuu, however, don't appear that way. What is different between them?
In Naruto, Kurama (the Nine-tailed bijuu) appears as chakra, as does Killer B's bijuu, Gyuki.
Other bijuu, however, don't appear that way. What is different between them?
The difference is that those are different stages of transformation, or different Jinchuuriki forms.
As you probably have seen, Killer B can also do a partial transformation, similar to the one shown on your image of Gaara:
Naruto, however, has not been able to do a partial or full transformation yet. He has been able to do a Tailed Beast Transformation, but in that one Kurama still appears as chakra:
As for the case of Isobu, he generally appears in that form because he was not sealed (at that moment) inside anyone. Thus, he appears in his full transformation form.
So basically, from what I've been able to gather, the different levels of transformation are as follows (I will use Naruto as my example):
- Initial form: in which the Jinchuuriki is simply enveloped in Bijuu chakra. Naruto's transformations shown in the first anime series generally fit into this stage.
- Version 1 of transformation: in which (in Naruto's case) up to three tails are are shown, in addition to the initial form's chakra cloak.
- Version 2 of transformation: the one shown in Naruto's fight against Pain, in which the Kyuubi's skeleton and up to (I think) 8 tails were shown.
- Partial Transformation: Naruto's partial transformation happened when Pain tried to seal him with Chibaku Tensei. However, in Naruto's case, he had no control whatsoever over the Bijuu. Different examples of this stage are Killer B's case (the image above) and Gaara's (the image on your question).
- Full Bijuu Form: Which Naruto has not been able to perform yet. Killer B however, has been seen to do this frequently and without much effort.
There are also the two most powerful transformations that Naruto was able to do (Kyuubi Chakra Mode and Bijuu Mode), but I do not know where those fit in the above 'scale' of transformations.
Plus, Version 1 and 2 are (as explained above) specific to Naruto's case. However, there is an intermediate stage between the initial form and the partial transformation stages for any Jinchuuriki, in which, proportionally to how powerful the form is, a certain (growing) number of tails appears.
When in initial form, the Jinchuuriki only accesses some of the Bijuu's chakra, but still needs little control over it. In Versions 1, 2 and in the Partial Transformation, if the Jinchuuriki does not have a good control over the Bijuu, he will lose control and consciousness, giving in to the Bijuu's will (which is precisely what happened with Naruto when fighting Pain).
To be able to do Partial or Full Transformations, the Jinchuuriki needs to have 'tamed the beast', and also to have very good control of chakra, in order to balance his (Jinchuuriki's) and the Bijuu's chakra.
On a side note, Naruto Wiki puts Killer B's Full Transformation Mode alongside Naruto's Bijuu Mode, giving them both the same name (Bijuu Mode). However, I am unsure as to why this is, because it seems weird that Naruto's Full Mode would look so different from all the other Jinchuuriki's.
Plus, his page there is the only one where both terms (Full [Bijuu number] Mode and Bijuu Form) appear. In Jinchuuriki 1 through 7, only the term Full [Bijuu number] Mode appears, in Killer B's case only Bijuu Mode (Tailed Beast Mode) appears, and in Naruto's case both terms appear.
Not sure how to do this but to add on to the previous answer, I suspect naruto's bijuu form is so different due to his uzumaki chakra which manifests in this form. An alternate possibility is kurama's chakra has a unique nature to it.
The form could be incomplete due to Kurama not having been fully sealed inside of Naruto unlike the other Jinchuuriki, since the other half was sealed inside of the Shinigami.
However, in episode 365 we see that everything within the Shinigami is unsealed, thus having the remainder of Kurama's chakra unsealed and possibly on its way back to Naruto and Kurama. If this happens, they may be able to do a complete transformation.
Even still, this may not be possible since a portion of Kurama's chakra is also inside of the Gold and Silver twins (Kinkaku and Ginkaku), which were both sealed away during the Allied Shinobi War at the ocean/beach front.
However, honestly, I think Naruto's incomplete transformation is far cooler than the other Jinchuuriki's complete transformations. It's bright and glowy too.
The reason behind Naruto's transformations is not that he only has half, but because Naruto and Kurama are not used to being completely linked. Kurama states that he can only use a percentage of the full transformation. Due to the war, they haven't had enough time to train to completely link the transformation. As for the other half, Minato has it inside of him, and Naruto reconnects the yin and yang chakras when he meets Minato.
You guys come up with so many theories but forgetting that each Jinchuriki's transformation corresponds to their own tailed beast.
However, for Kurama's case, it is mentioned before that its form is unique only to its current host.
For all, I believe that it's already in a complete form. If not why would Ashura want to fight a perfect Susanoo against Indra with the same tail beast transformation as what Naruto is doing in manga chapter 670.
I think Kurama appears in this form, because of the form of sealing and the amount of chakra that is sealed inside Naruto. Like we know from the manga (chapter 643), Minato just sealed the half of Kurama inside of Naruto and the other half inside of himself. Because of this, Kurama probably just appears in Chakra-mode.
Gyuki probably appears in Chakra-mode because he is linked to Killer Bee (they are friends), so Bee only activates Chakra-mode, because in this mode his strengh is equal with the Raikage's (perfect precondition for their lariat). And if Bee is fighting alone it's enough to deal with his opponent.
(Please forgive me if I wrote this a little twisted and with spelling mistakes, but I'm a German and I'm not the best English-writer.)