Kyubi is a fox Yo-kai that stands about twice as tall as Nate at 220 cm, and is covered in thick, golden fur with white belly and paws. Its chest is covered in a thicker patch of purple fur, surrounded by a yellow "trim" around his shoulders, with four wispy hairs sticking out. Kyubi has nine tails, each tipped purple, and sports long nails of the same color. Its muzzle is long and pointed, like its golden-tipped ears, and on its face are markings resembling a kitsune theatre mask, with tomoe eyebrows.
In the anime, Kyubi has taken human form several times. In human form, Kyubi is a young boy about the same age as Nathan. He wears a blue sweater vest over a white shirt and black shorts. He has green eyes and grayish tousled hair, with two strands standing up and nine strands in the back that resembles his nine tails. Sometimes those two strands become ears and Kyubi's nine tails appear when he gets excited or the glamour starts to fail.
Kyubi has the ability to control fire. He also has the ability to shapeshift.
In the anime, Kyubi can charm almost anyone, which creates a "Kyun ball" which Kyubi collects. It is suggested that these balls are a piece of the heart of someone that Kyubi has charmed. In the game, he has an ability called "Sense of Smell" which allows him to deal damage not caring about the typing.
In the games, Kyubi is arrogant, serious and cold, but not unjust. While he spoke condescendingly to Nate and Whisper and openly mocked Komasan for his timidness, he reveals after the defeat of Massiface that he is in fact, working to aid Nate and Whisper and hopes that they will be able to stop what was coming. He is also manipulative and openly admits to this, having lured Nate to the Construction Site to pit him against Massiface.
In the anime, he is more antagonistic, but also more comical, featuring a narcissistic and womanizing personality; Kyubi has tried to charm Katie, but it appears that Kyubi was the one charmed by Katie instead.
In the games, Venoct and Kyubi are treated like opposites. For example, in the second game, Kyubi likes the Fleshy Souls while Venoct likes the Bony Spirits. In the Oni update of the second game, Kyubi got a dark form called Darkyubi while Venoct got a light form called Illuminoct.
Also in the games, the Crimson Master Kyubi is somehow related to the science teacher Mr. Barton. Fans speculate that the science teacher is that Kyubi but in his human form. The possibility of him being Kyubi was confirmed when the quest, Miwaku no Kyun Kyun Daisakusen (The Charming Charm Operation?) showed that Kyubi gave the Kyun balls to the science teacher because he thought he was the Crimson Master.
To befriend Kyubi you must first complete the post-game quests "Flower For The Shrine", "An Offered Sword" and "Take Out Tengu!" (see Dromp, Zerberker and Tengu). Once you're done, go to the Springdale Elementary rooftop at night and take the quest "The Legendary Kyubi" from Kyubi himself. Collect a Golden Tofu from Mama Aura in the 3rd or 4th Circle of the Infinite Inferno (if you didn't already), then use the Mirapo in the back of Mt. Wildwood Shrine (not the regular one by the Eyepo) to go back to the day of the festival. Offer the Golden Tofu at the shrine, and Kyubi will appear to fight you. Once you beat him, he'll automatically befriend you.
In Yo-kai Watch 2, you talk to a girl in Mr. Barton's science lab to activate her quest
Talk to a student in the front doorway of the school.
Talk to a student on the outer staircase inside the school.
Talk to a girl at Shopper's Row, Fox Shrine Road in Old Springdale.
You may or may not be forced into a Fox Trot Wedding Dance when traveling to the present
Talk to the girl who gave you the quest again. After talking to Mr. Barton this should spawn Kyubi on the school roof at night.
Fight Kyubi to complete the quest.
Wait 1 day after the quest in order to fight him again to befriend him if possible. You can't use food items on him. Kyubi doesn't befriend like other Yo-kai, after the battle, make sure to read Kyubi's next few text boxes, as these will tell if you've befriended him or not. It may be possible that you must defeat Kyubi faster to have a better chance to befriend.
In EP018, Kyubi arrives in the human world on a mission to collect the hearts of humans. At this point, Kyubi has already charmed 99 women and only needs one more to become a senior Kyubi. Then, he spots Katie and decides to make her the next target. Over the course of his attempts, however, he ends up falling for Katie.
In EP027, Kyubi was seen in Yo-kai-lifornia where he was among the Yo-kai waiting in line for the release of the new Yo-kai Watch Zero.
Nate, Whisper, and Jibanyan formally meet Kyubi in EP031, where Directator forcibly involves him in his film interpretation of "Journey to the West." Kyubi gives Nate his Yo-kai Medal as part of his introduction.
Kyubi appears in EP032 alongside Dandoodle after Nate expresses a desire to be popular with girls like a model. After the two popular Yo-Kai argue over what characteristics would get Nate noticed by girls, they have a competition in teaching Nate how to gain a girl's affections.
Kyubi is summoned in M01 during the final battle, along with the others Yo-kai, fighting against Dame Dedtime and her Wicked. He even saved Manjimutt from one of the Wicked.
In the first game, Kyubi lures Nate/Katie to the construction tower at night. At first, it seems as though Nate/Katie is about to face Kyubi himself, but instead another Yo-kai, Massiface, approaches Nate/Katie to fight them instead. After Massiface is defeated, it turns out that Kyubi was trying to get rid of the giant Boss Yo-kai, and decided to use the player as a way to take care of Massiface.
He later appeared when McKraken's goons started to flood into Uptown Springdale, taking care of a few of them to allow the player the window to create the seal for the Yo-kai Elevator.
Hits faraway enemies. When charged, does more damage.
SPR +45 (Level 10)
"Kyubi" (Japanese: 九尾,Kyūbi) translates as "nine tails".
Kyubi is based on a kyūbi-no-kitsune (Japanese: 九尾の狐,kyūbi-no-kitsune) or nine-tailed kitsune (supernaturally-endowed fox). As they grow more powerful with the passing of years, kitsune grow a new tail with each century of age: once they grow their ninth and last tail, their fur will turn white or golden, and their power will reach its maximum. Kyūbi-no-kitsune is gifted with immense wisdom, powerful magic abilities, and can even see and hear everything in the world. They're especially proficient in weaving illusions, and wielding spirit flames called kitsune-bi ("fox fire"). Like tanuki, all kitsune can also shape-shift, though they prefer to take on the appearance of beautiful men and women.
Making his first appearance in EP018, Kyubi has his medal registered in the Yo-kai Dictionary despite not meeting Nathan formally until EP031.
It's debatable if anyone that doesn't possess the Watch or can see Yo-kai can actually see him. The people who were dressed up as zombies in the haunted house can see him, possibly in a similar level as Manjimutt and Dandoodle. Yet when interacting with Nate, no other humans notice.
Though it is possible that the humans as zombies in the haunted house can see Yo-kai, like with Amy and the lead singer of Next HarMEOWny.