Kazuki is the scion of the noble Fuuchouin family, and his fighting abilities derive from the family school, which emphasizes grace (麗). He is graceful and charming, and is often mistaken for a woman because of his long hair and feminine face. But when angered, his fury is such that his notorious other title is "Prince of Fear". He's also one of the characters who's frequently drawn super deformed, as he's the butt of many gay / woman jokes. It does not help that he sometimes does wear women's clothes in his line of job as an information-seeker, as is shown when he coerces information about the Hall of Hell out of an Ura follower in a bar.
Kazuki is also often depicted as a naïve person in terms of his relationships. He trusted his friends even after they betrayed him, leading to him being taken advantages by the likes of Saizou Toufuuin and Toshiki Uryuu. However, it is also his unerring trust that keeps his friends and followers to flock to him. Due to his job as an annaiya or information seeker, Kazuki knows a lot of things concerning the Infinite Fortress. His origins as the heir to a famous and ancient martial arts' school provides him with the privilege of knowing the truth about the estrangement between the Miroku clan and Mido Ban, as was shown during the Hot Spring Rest chapters. Kazuki also knows a lot about religions, history and cults, and undoubtedly is one of the wisest people in the manga.
As one of the Four Kings of VOLTS during its heyday, Kazuki was respected and feared by many, and also known outside underground circles due to his noble past. Even without using his Stigma his powers, rendered from the Fuuchouin arts, were already formidable enough to send enemies quaking. He was often considered the most powerful of the Four Kings, as was stated by Hevn during the IL Retrieval arc, due to his own fighting prowess, his connection with the ex-Fuuga members (who were themselves very highly placed in the VOLTS hierarchy, with Juubei alongside Kazuki as his aide and Sakura as MakubeX' caretaker) and his knowledge of the dangers of the Beltline and the nature of its people. However, Kazuki's gentle and compassionate nature, when not using the Stigma, often made him less confident to face his enemy, as was shown when he fought three of his comrades form Fuuga days: Kakei Juubei (although the other man ended up blind, Kazuki himself received injuries particularly on his left eye), Toshiki Uryuu (Kazuki lost out altogether due to Toshiki's being more informed about the powers of the God's Design pseudo-Tarot cards) and Saizou Tofuuin (Kazuki pleaded for rational thought with Saizou continuously before Saizou's attack on Ren and Emishi snapped Kazuki's patience and activated his Stigma).
In the Shinjuku area, Kazuki is an annaiya, or information seeker, who searches for information or a person for a price. This is shown when he helps Paul to seek for the whereabouts Takeru Teshimine, Ginji's foster father and former leader (and supposedly, symbol) of the Lower Level before VOLTS came into being. It is during this moment when he realizes that the forces of the Kokuchouin clan is at work in the mysterious depths of the Infinite Fortress. It is probably from his career as an information-seeker that he seems to be the most informative Lower Town resident (excluding MakubeX, the Gen Pharmacist and Kuroudou Akabane) about the mysteries of the Infinite Fortress. While fighting against Saizou, who boasted of his strength after he activated his Black String seal, Kazuki explained to him that the 'Stigma' is not merely a device to increase one's strength. He said that the mark is a sign that one is chosen by the Infinite Fortress to achieve a specific mission, even in the face of death. This property was manifested in his final fight with Yohan.
As it turned out, Yohan was Kazuki's younger brother. In fear that the Stigma Yohan bore would be an ill omen to the clan (Yohan bore the Stigma since birth, whereas Kazuki, on the other hand, obtained it when he challenged the Beltline, thus was recognized as a powerful man in his own right), the patriarch of the clan initially wanted to kill the infant. Under the pleas of his mother, Yohan was instead given to the Ura house for adoption. As for Kazuki, he was told that the child was still-born. After learning the truth, the older brother tore out his "Stigma" eye and used a technique which he shouldn't have known: the Phoenix (apparently, as Kazuki's mother mentioned, this skill should only be passed down from mother-in-law to daughter-in-law). Using this skill, Kazuki solved the misunderstanding between his younger brother, Yohan. He tells him that he was forgiven by everyone. Both brothers are knocked unconscious. Yohan awakens to find his Stigma has vanished.
It has been revealed that the enemy clan that had destroyed Kazuki's clan, the Kokuchouin, was actually related to Kazuki, under an elaborate clan system that involved the Fuuchouin (known as the Omote, or the 'Outside' clan), the Kokuchouin (known as the Ura; the 'Inside', hence 'Hidden' clan), and Saizou Toufuuin's clan, the Higashi Fuuchouin ('East Fuuchouin') and Akame's school, the Nishi Fuuchouin ('West Fuuchoin'), which is thought to be more of an extension of the Kokuchouin. Of these schools of string manipulators there was a traditional recognition that the Omote Fuuchouin was the superior clan.
Relationship between the Ura and the Omote is always fraught with conflict and envy. The Ura is not allowed to appear in public. During the Ura-Omote clan war, five Ura fighters spoke to Kazuki disdainfully about the beauty and the arrogance of the Omote and how, with the wipeout of the Omote, it would be the 'shadow' of the Ura that would now rule the clan. It was also shown that the Ura was abstained from joining the traditional duelling contest between the houses due to this matter. The fact that Yohan is able to 'copy' every string martial art that he sees did less to calm the suspicions of the other clans. Quoting Kazuki's father, 'The Ura are shadows, and must not come into the joyful light of this festival'. The enmity survived even to the days of Yuuri and Maiya of the Kokuchouin, who belittle Kazuki's noble origins when they confronted him, MakubeX and the GB duo upon their entrance into the Beltline. Yuuri was especially harsh in saying Kazuki was the cause for Saizou's (emotional) sufferings all these years.
The Ura has been described as a survival mechanism that allowed the Fuuchouin Martial School to survive for more than a thousand years. In every time of chaos and wars, in which presumably the Omote, as the visage of the clan, would be wiped out, it would be the Ura who would carry on the bloodline and ensure the school's survival to modern times. The gist of this situation is further enhanced when it had been revealed that all Ura practitioners are willing to die for their arts, thus ensuring the life of their companions and the consequent death of their enemies. This has been described by Kazuki by comparing the Omote to a beautiful swan admired by many, while the Ura was the murky shadows of the water on which the swan floats. Arguably this complex love-hate relationship had led to the Fuuchouin war, catalysed by the leadership of the so-called Demon Prince of the Strings, Kokuchouin Yohan.
Though his fighting skills are far above average, Ban often discredits them. Also, it can be noted that he often ends up badly hurt even if he wins a fight. Sometimes, he even loses them as well. (To be fair to him, Ban often gets whacked up too before he wins a fight.) To emphasize his "mid-tier" status, even as he was berserking as the Prince of Fear, Shido Fuyuki was able to stop him easily by grabbing his arm firmly without using any special powers. Indeed, Yohan mentioned to the Voodoo King that perhaps the Beastmaster would be an even greater threat than Kazuki. However, this is mainly because of the influence of Shido's Chimera, a relic of the Maryuudo and one of the three keys to Babylon.
The arts can be described as integration of the feminine movements with surprising amount of power. Juubei had described Kazuki's battle movements as an intricate dance: as such most of the ancient martial arts described in the Getbackers series had been described as such, particularly those of Kakei Juubei and Toshiki Uryuu. Accounts vary as to how many years the practitioners of the Fuuchouin had to wear the female kimono in order to obtain the necessary grace to execute the techniques: in the Hot Spring Rest arc, Kazuki stated a period of 15 years, while in the Get Back The Lost Time arc, the period was 12 years. It is also not evident whether this practice apply to every practitioner of the arts or only to certain talented individuals, or even only restricted to those of the main line of the Fuuchouin itself. On the other hand, the Higashi-Fuuchouin and the Kokuchouin clearly did not practice this tradition. Amongst the feminine arts practiced (at least by Kazuki) were dancing and the playing of the koto, long regarded as a feminine musical instrument in traditional Japan.
The reason for Kazuki's strings' unnatural strength is the amount of vibration applied on them by Kazuki's fingers. Though it is hard to imagine how to make the countless strings vibrate whilst performing the intricate techniques, Kazuki seems to be able to do so naturally (One theory is that he focuses his "qi" through his strings. Indeed, he could often be seen concentrating before unleashing his moves. If so, Juubei's notion that 'the Fuuchouin and the Kakei are derived from the same style, which, if combined, will have enormous power' is true, as the Kakei-ryuu is often shown as a 'qi' manipulation technique). This vibration technique must be particularly potent as Kazuki's string shields can protect him from virtually any physical attack, as was shown when he protected Ginji and Kuroudo from Semimaru Kanade, the most powerful of the Kiryuudo 7, in the 'Get Back the Eternal Bond' arc, and even explosions, as was shown when he, Shido and Ren were caught off-guard by Masaki Kurusu in the latest arc. However, it has been shown that this shield can be broken by sufficient strength, or completely by-passed (by Masaki's "light", for example).
Among the Fuuchouin-ryuu techniques commonly used by Kazuki are:
Apparently, the strings can also be manipulated to resemble actual weapons, i.e. spears, axes; this technique, which remains unnamed, is almost exclusively used by the Ura-Fuuchouin initiates, most evidently bu Yuri Kokuchouin. However, during Kazuki's duel against Saizou, he manipulates his strings to form giant balls from which any strand (effectively resembling a rocket) can escape and attack his assailant. Another Ura-Fuuchouin technique involves using strings to change the external appearance of oneself. Extensively used by Maiya Kokuchouin and, to a lesser degree of virtuosity, Akame of the Mugenjou, the technique is said to originate from the Nishi-Fuuchouin. Maiya is also able to wrought string puppets of herself. By using the Infinity Fortress dimensional rift, she is able to hide in another dimension and subsequently used the self-regenerating puppets to attack her enemies to death. Due to this she is counted stronger than her berserker brother Yuri. However the strongest Ura technique is credited to Yohan Kokuchouin, in which his movements alone is able to nullify the combined effects of the Flower•Bird•Wind•Moon. His ultimate, using string projectiles in shape of origami cranes, is able to render explosions and is almost impossible to evade due to the sheer number of the cranes.
An unnamed technique involves constructing a wall of strings around a person or a group of persons, effectively restricting the movement of the targets. Probably derived from the Cursed Binds, the seemingly basic technique can even stop the Getbackers' progress when used by Saizou to impend their progress at the end of the Queen's Cup Challenge arc.
Unique techniques (shown only once, usually include a series of number to imply the technique's sequence in the Fuuchouin-ryuu) include:
There are also a few healing techniques in the Fuuchouin-ryuu, but most concern the effects of the Black Strings. Among them are:
There is also a separate technique used by the Fuuchouin 13 Strings, the bodyguards of the Fuuchouin patriarch. The tecnhique revolves around plurality, in the sense that the strings used are controlled by many people at once, giving extra strength and flexibility. One of the techniques used against Juubei was Flower-Viewing, in which multitudes of strings were bound around the body of the victim, supposedly suffocating him or her to death: effectively the Coffin technique handled by 13 individuals.
It has been revealed during Kazuki's duel against Youhan that the ultimate technique of the Fuuchouin-ryuu is #99, the Flower•Bird•Wind•Moon. The technique is actually composed of four separate fighting techniques derived from natural phenomenon connected with the name. The techniques are:
It is originally thought that the essence of the ultimate technique lies in 'Moon'; thus the strongest Fuuchouin-ryuu technique would be the 'Empty Moon'. However Kazuki's mother remarked that the true essence lies in 'Bird'—which is beautiful like the flowers, moves fast like the wind and can fly high like the moon—and it was to this assumption that the 'Phoenix' technique was derived from. The technique itself was called 'Fuuchouin-ryuu, side chapter', remarking its incandescent position as a technique unknown even to the patriarch of the Fuuchouin clan.
In the anime, Kazuki's true strength is never shown, (or rather downtoned, for the sake of the children in the audience) albeit it seems that a lot of people fear him, or at least heard of his (notorious) prowess as VOLTS' "Ito no Kazuki". In the manga, the true essence of his battle potential (or rather, the strength of the Fuuchouin-ryuu) is regularly shown, in order to give contrast to his gentle demeanour. For instance, Kazuki can rip away arms and legs, bind people to the point of losing the nervous system, sew people's eyes and mouths for showing disrespect before him and put people under 'cursed binding strings' (note: not black strings) which cut people into seven pieces if they are to move a muscle. Kazuki is one of the fighters which earned the respect of the Kiryuudo 7, and remarked as 'able to fight one against hundred' Kiryuudo warriors, which are far stronger than human. In 'Get Back the Lost Time', when Kazuki totally lost self-control in his 'Stigma'-induced Prince of Fear mode, he is shown smiling gleefully amidst bloody Ura fighters, many of which are already decapitated by his strings, with blood spattered on his face. Before that, during the 'Oath' Rest arc, he spends a few sleepless days pursuing people connected to the Ura and killing them mercilessly in the backstreets of Urashinjuku, as revenge for the taking of Juubei, Uryuu and Sakura. In the final arc, he is depicted as able to destroy a large section of the Beltline simply with the effects of his duel against Saizou.
Aside from the usual white strings, Kazuki also uses a special string, the Red String. In the Divine Design arc, when Kazuki's soul was trapped by Uryuu, the Red String flew from his side to Juubei so that Juubei knew that Kazuki was in grave danger. In an intense moment it is revealed that the Red String is a symbol of an oath between Kazuki and Juubei, apparently made after the massacre of the Fuuchouin clan, that whenever Kazuki 'strays' (as is shown when he is under the Divine Design spell), Juubei is to kill him to save others from Kazuki's purges. Juubei, however, does not kill Kazuki in the moment but let his blood, derived when he received the 'Comet' from Kazuki, reddens Kazuki's white strings so that the illusion of 'red' strings will remind Kazuki of their oath and release his ensnared soul from the Divine Design world. In the manga, Kazuki also used the Red String to summon Saizou Toufuuin, another member of the Fuuchouin String School, to him when the Fuuga team was assembling to get ready for the tournament in the Voodoo Child arc.
In Japanese culture, the "red thread" has a symbolic meaning comparable to the ideology of "soul-mates" in Western culture. The fact that Kazuki's Red String represents his oath with Juubei had been taken by fans of the series to imply a romantic relationship.