Sora's Jinchūriki Forms

When the Nine-Tailed Demon Fox attacked Konohagakure, it left a lot of chakra in the air, which was later gathered by Kazuma, one of the 12 Guard Ninjas of Fire, who wanted to create a Jinchūriki weapon for Konoha. After five years of experimentation, he finally was able to implant the demon fox's chakra into the cells of his son, Sora. Because Sora does not have the Tailed Beast sealed within him, but only has his cells combined with its chakra, he is refered to as a Pseudo-Jinchūriki. And since Sora does not have the actual Nine-Tailed Demon Fox inside of him, he doesn't have as much chakra as the demon fox would usually generate when Naruto is in his demon fox cloak, nor can he control it, instead being overwhelmed by the fox chakra's destructive instinct; when in his fox cloak, Sora threatens to kill anyone who stands in his way.

Jinchūriki Form
Unlike Naruto, who has a stable and controlled combination of his own chakra and the Nine-Tailed Demon Fox's chakra (because of the Fourth Hokage's seal), Sora can't control the chakra added to his cells. To stabilize this, his father applied a sealing jutsu on Sora several times to keep him and the chakra under control.

When Sora feels frustrated or is in a state of great anger, the chakra can change his right arm into a demonic form. It would seem that he is not aware at all about the change of his arm, and has first noticed it when his father told him.

Because the Nine-Tailed Demon Fox is a chakra monster, the small amount of its chakra implanted within Sora can react to the chakra of the real Nine-Tailed Demon Fox inside Naruto as it somehow called out to him when Naruto was about to be killed by Fuka.

One-Tailed Transformation
When his father would stop applying the seals or when he completly releases it, he uses the Five Elements Unseal, which the chakra can run loose and slowly take over Sora's body.

Like Naruto, when the chakra is released from Sora in large amounts, a demon fox cloak will form around Sora, initially and slowly he will begin to grow a chakra tail. In addition, like with Naruto, during this transformation, Sora's hair becomes spiked, his canines longer and sharper, and his eyes turned to slitted foxlike eyes. Also in this form, the chakra surrounding him damages the people around him.

Due to being a Pseudo-Jinchūriki, Sora has some different features from Naruto in a similar state (besides the arm) including spiked projections growing from his cheeks.

At first when the chakra was taken over his body was he in pain, and could slightly control himself, but slowly he began giving in to the urges of the demon fox's chakra, and gains a will to kill and destroy everything, a problem Naruto never displayed until the fourth tail emerged.

Three-Tailed Transformation
Skipping the two-tailed form, Sora grows three chakra tails. Not much is known about this stage, only that he, like Naruto, begins crouching on all four.