Kōji Tsujitani (Japanese), Jerome Fifty-Seven (English)
Itsuki has white pale skin, long, teal hair that is parted down the middle with short bangs pushed to the sides of his face. He wears a red sleeveless undershirt, white sleeveless loose tunic, and a yellow obi sash tied around his waist.
In flashbacks, he is seen with his hair tied back in a ponytail adorned with a ribbon and wears a traditional Chinese-style outfit reminiscent of Hiei and Kurama's clothes in the Dark Tournament but in a traditional Japanese-style. He wears a purple long Japanese vest with a pale yellow long sleeved traditional kimono shirt, a matching traditional pants, white tabi and a matching geta sandals.
In his first meeting with Sensui in his high school years, his hair is loose like his current self and wears a modern casual outfit.
Itsuki is renowned for his unwavering love and loyalty to Shinobu Sensui, which budded from a morbid fascination with the young Spirit Detective's ruthless methods of eradicating demons and his immaculate moral character. Itsuki is familiar with all of Sensui's alternate personalities, stating that he's especially fond of Naru; Sensui's emotionally vulnerable female personality. However, this does not rival his affection for Sensui's original, untainted personality. Shinobu never visibly reciprocates Itsuki's love on screen. Itsuki displays an externally stoic, relaxed, and philosophical demeanor; rarely showing signs of agitation.
Itsuki also has a twisted sense of humour and enjoyment, as he states that as Sensui's mind became more and more twisted after Sensui's last Spirit Detective case, Itsuki did nothing as he enjoyed watching his soul darken.
Itsuki was the first demon which Sensui spared from death. After having beaten Itsuki into submission Sensui offered the demon one request before he could kill him. Itsuki replied that his favourite television show was going to air it's final episode the next day and as such wishes to be left alive long enough so that he may view the series finale. This request sparked an interest towards the demon since Sensui was also watching that same television series. Impressed by Itsuki's laid-back and matter-of-fact behaviour Sensui decided to let the demon live, slowly the two became best friends and partners against other demons. It was Itsuki who told Sensui of demon world and also of the portals which connected it with the human world. Itsuki had accompanied Sensui in his final mission as spirit detective: stopping the Black Black Club's underground demon trade ring. The two had successfully infiltrated the headquarters of the Black Black Club and decided to spilt up to cover more ground. When Itsuki had regrouped with his partener he had found Sensui drenched in the blood of the club members. Sensui had murdered every member who had participated in the Black Black Club's yearly ritual of bathing in the blood of several demons which they had tortured to death. From that moment on Itsuki remained the close friend and confidant of the mentally disturbed Sensui, who at developed an ardent hatred towards humanity and several personalities. They spent years planning the extermination of the entire human race by means of a portal that would allow A and S class demons to enter the human world.
Chapter Black SagaEditItsuki's objective is to open and stabilize the portal that would lead the demons into Human World. He doesn't participate in the battles, but keeps Yusuke's friends contained in an alternate dimension while Sensui fought Yusuke. He explains his feelings for Sensui, as well as the truth behind his separate personalities. After Sensui is defeated by the Raizen possessed Yusuke, Itsuki tells the group that Sensui was going to die soon anyway from a terminal illness. Afterward, he takes Sensui's body through a portal, for them to spend eternity in seclusion and peace.
- Dimensional Travel ( ディメンション ・トラベル , Dimenshon Toraberu ), translated as Dimension Travel : Itsuki possesses the shadow hands, a powerful demon ability unique to Yamanate, as Kurama calls him in the anime, that allows him to travel between dimensions and to create dimensional portals. It also allows him to control demons from different dimensions, such as in the fight between Yusuke and Sensui. These shadow hands are also why he is nicknamed the Dark Night Stroker. In some video games he can actually strike people with the shadow hands, as well as heal himself.
- Gatekeeper (闇撫・の・樹, Yaminade no Ki, literally translated as Establishment of Dark Comfort): Itsuki guards the inner depths of Demon World.
- Uraotoko: Called Ura Otoko (裏・男, translated as Reverse Man) in the original Japanese, this vaguely-humanoid creature is Itsuki's pet and bears a startling resemblance to the Umibōzu (海坊主, literally translated as Sea Buddhist Monk) of legend and is a veritable pocket-dimension unto itself. Given all the debris seen within it, it can be inferred that this creature has existed for a long time. It was only defeated when Kuwabara was finally able to call out his Jigen Tō and cut through both Itsuki and the Uraotoko in his attempt to escape it.
- Telekinesis: Itsuki briefly demonstrated this ability when he, apparently through psychic means, mentally lifted a late Sensui into mid-air; ceasing when he was able to cradle the spirit detective's body in bridal position.
- Morph: As seen just before Yusuke fought Sensui, he can merge with whatever he comes in contact with, taking on its properties as he does so.
- Itsuki is one of author Togashi's favorite characters; he stated after the series ended that he wishes he had been able to expand on the character's twisted psyche. He also noted the portion of the plot where Itsuki speaks inside the Reverse Man to be his favorite of the series because it reflects how the mangaka was feeling at the time.
- Harry McDougal, from Outlaw Star, is similar to Itsuki in appearance.
- Since Sensui's Seven each represent one of the seven deadly sins, Itsuki represents Lust in his desire for Sensui and manipulating him towards the path of depravity.
- Itsuki, aside from Elder Toguro through Gourmet, is the only demon in Sensui's Seven.
- Itsuki is the only member of Sensui Seven that does not fight the main characters. His fighting ability is relatively unknown, although he is a playable character in several Yu Yu Hakusho fighting games.
- Itsuki is also similar to one of Togashi's characters from Hunter x Hunter, Knov, whose powers allowed him to create portals in another dimension by his will.
- It is implied that Itsuki, along with Tsukihito Amanuma and Elder Toguro were the only members of the Sensui Seven not to be shown Chapter Black, instead Itsuki followed Sensui due to his obsession and long history alongside Sensui.
|e v||Sensui Seven|
|Members:||Shinobu Sensui | Itsuki | Kaname Hagiri | Minoru Kamiya | Kiyoshi Mitarai | Tsukihito Amanuma | Sadao Makihara | Elder Toguro|