Nanashi appears as a tall ominous figure, wearing a long black cloak that fades as it goes down, a matching black hat, resembling a fedora or homburg. His hands are pale white and rather bony. He is constantly surrounded by a dark aura. His most notable feature is his face which is white, his eyes have black scelrae and glowing purple pupils. Later it is revealed that this is actually a mask and underneath is colored dark purple.
After absorbing all of the malice stored within Mana and herself, Nanashi transformed into a giant monstrous baby with pale pink skin, pointy ears and few strands of black hair across his head. He has four eyes, all having black sclerae and luminescent irises, with the lower pair being blue while the upper pair are yellow.
Nanashi's true form is that of a small, dark purple creature, whose eyes have the same color as the pupils of his masked form.
For the majority of the anime, little was known about Nanashi's personality, other than he being very mysterious and enigmatic. He usually speaks in strange sentences and cryptic phrases, but can also speak normally if he wants to do so.
Nanashi is a very intelligent individual, able to manipulate humans and yōkai, even powerful ones such as Backbeard, from the shadows, using any means at his disposal. Nanashi is also very patient, as he watched over Mana's bloodline for centuries, in order to find the ideal vessel for himself.
Nanashi's end goal was to destroy both humans and yōkai, and he would stop at nothing to achieve this, gathering as much malice as possible from them both, going as far as to create several world-class threats, without any apparent remorse.
Whenever Nanashi collects enough malice, he infuses it into Mana in the form of seals, without her being aware of it. By Nanashi's own account, he needs five of these seals to complete his objective, which he succeeds in achieving in the 48th episode.
Upon transforming into a giant oni baby, Nanashi seemingly loses the ability to speak words normally and only cries like a baby would. Nonetheless he retains intelligence to recognize Kitaro as his enemy. His true form also cannot speak, but remains intelligent.
Nanashi is at the end a broken soul, being surrounded by nothing but hatred, and being denied the right to be born and loved, causing him to resent everything, but yearning for the love, compassion, and name that he never received.
A long time ago, Fuku and an Oni were expecting a child, but their respective families disapproved of their relationship and falling in love with each other. Despite them telling it can wait after the birth of their baby, the families both considered their love a sin, and killed them both with the unborn baby still inside her. After their bodies were hung on top of a mountain, all of the malice of the humans and yōkai went into their blood, and resulted in the spirit of the baby being born without a name, and took form with all black with a white mask covering his empty face resulting in the creation of Nanashi, a yōkai with hatred for the world.
He is first seen in the opening behind Mana in the train station scene and at the end of episode one, where he shoots Kitarō in the back with an arrow from a rooftop. The arrow has a pentagon shape carved into it. In episode two, Medama-Oyaji states that it is not just a star mark; it's the flow of the five elements that make up everything. In addition, he informs everyone that an upside down pentagon represents a connection with Jigoku - that someone carved this shape into the arrow and targeted Kitarō. At this point in time, it is unknown to the Kitarō Family that Nanashi was behind the attack. At the end of this second episode, Nanashi is seen placing a sheet on the ground with the pentagon symbol, awakening Tantanbō. After Tantanbō and the others affiliated with the Yōkai Castle are defeated in episode three, Nanashi is seen watching over Kitarō and the others before turning away.
He returns much later and is seen in the beginning of episode #11, where he releases the seal placed on the Kaname Stone and awakens the 808 Tanuki. When the Tanuki and the Yō-Kaijū are defeated at the end of episode #12, Nanashi is seen directing the malice from humans that were under the Tanuki's influence into Mana's right palm. It is the same palm that held the power of the Kaname Stone after she pushed the stone off a ledge in order to break it. A red character symbolizing the element of wood, "木" (ki), appeared on Mana's palm before vanishing. Mana collapses soon afterward. The next morning, Nanashi is seen watching Mana from an electricity pole, singing an eerie song about a hollow vessel while a sequence of a blue-eyed woman being chased down by two men with a sword is shown.
In episode #19 he appears behind a middle school student sitting by a shrine, who complains about going to cram school in the summer, wishing his teacher was dead, Nanashi's tongue extends and gives the boy a quick lick on his back. It is also revealed that he has the power to resurrect yōkai defeated by Kitarō. He resurrects Tantanbō, Futakuchi-Onna and Kamaitachi in addition to Miage-Nyūdō. With Miage-Nyūdō as the principal, Tantanbō and the others serve as teachers at the Obake School where disillusioned young people can be turned into obake. He finally shows himself to Mana but disappears soon after as a silent silhouette passing through her body. Kitarō defeats Tantanbō and the others once more and asks him who was responsible for their revival, to which Tantanbō immediately replies that Nanashi revived them. Kitarō asks who Nanashi is, but Tantanbō ignores the question and states that Kitarō cannot win against Nanashi before his body is destroyed again. Later, Nanashi appears before Kitarō, appearing as a raving madman sprouting half-intelligible threats towards the young yōkai. "To consume you is my pleasure!" was his last phrase before vanishing again. Medama-Oyaji says that as Nanashi's name implies, perhaps he has no name. Kitarō is still left perplexed about Nanashi's existence as the episode ends.
In episode #25, Nanashi is first seen in a dark room. A phone on the floor receives texts that target its owner, pushing the owner to die. A toppled chair and a pair of legs are seen dangling: the owner has committed suicide. Nanashi appears from the corner and looks at the phone, removing his mask and smiles as he extends his tongue and to begins licking the phone. He is next seen within Mana's phone and watches her and Miyabi as they download the Curse App. He begins talking about a hollow vessel becoming real. The Curse App's victims increase, and Nanashi is seen again atop a tree with a noose set on one of its branches. He states that cursing is wonderful and that it reveals the depths of the soul and a person's malice. He bends to his right and extends his tongue to lick the noose. Mana gets a hold of her phone again in an attempt to contact Neko-Musume, but is quickly surrounded by Curse App victims and is prompted to enter a name into the app. Mana, worried of what may happen if she enters Karin's name once more, enters her own name into the app and Nanashi appears behind her as she does so. However, he vanishes and is not seen again until after Kubire-Oni appears and is defeated. Mana's phone is returned to her and Medama-Oyaji claims that it is now safe. Afterward, Nanashi stands on top of a tower, humming about cursing others and states that dark thoughts will never cease until "the world of man comes to an end." He leans back and raises his arm to the sky and it simultaneously appears out out of Mana's phone. Mana is asleep and unaware of this. Nanashi's hand reaches out to her forehead from within her phone and marks her forehead with the character symbolizing the element of fire, "火" (hi). He counts this as two and asks when will the day come when five are gathered as his arm retreats back into the phone.
In episode #27, he appears and shields Agnès from Adél's attacks. Although he points to a certain direction, Agnès states that she will choose where she goes on her own and flies off on her broom. Nanashi then watches as she leaves and says, "where you proceed is my desire." He appears again on top of a building, speaking about war.
In episode #37, he takes all of the human despair from when Backbeard turned them into yōkai, and only showing from his head, uses his extendable tongue, and places the malice into her left leg, with the character symbolizing the element of Earth, "土" (do). That led to him only needing two more seals left and vanishes without her knowing at all.
In episode #42, he is at the trial area saying how Kitarō is bound by law and moved around in a creepily way and vanished, towards the end of the episode, Nanashi stops time, and levitates Mana from the ground, and takes off his mask to add all of the malice from the trial, and placed it into her left part of her head, with the character symbolizing the element of Metal, "金" (kin). Nanashi resumes time, but gave Mana more fear of him being around her.
In episode #48, Nanashi gathers all of the human and yōkai despair and hatred, along with Kitarō's and Mana's and places them on the right part of her forehead, with the final character symbolizing the element of Water, "水" (shuǐ). Since it was complete, Nanashi levitates Mana and puts her in the pose of the Wu Xing pentagram, and reverses the elements and the pentagram into the upside down pentagram, and proceeds to swallow all the despair and hatred malice, along with Mana, and gained more strength. This resulted in Nanashi growing huge and transforms into a gigantic baby, after his transformation, he went after Kitarō, and overpowered him barely, when he uses his Chanchanko to protect himself and when Medama-Oyaji used finger guns on him tipping him and pushing Kitarō far away. After Nanashi got the chance to recover, he smashed Medama-Oyaji with his hand, and disintegrates the surroundings, leaving the area desolate with Kitarō still remaining alive upset at the lost of his father.
In episode #49, Nanashi continued to remain in the spot that he disintegrated, while Kitarō was giving up after Nanashi killed Medama-Oyaji. After Kitarō got the boost in motivation from Nezumi-Otoko, he went back and used Finger Guns on Nanashi allowing him to enter inside it. Inside, Nanashi summons many arms out of a black hole and grabs Kitarō to a water-like area, where he learned about why he gathered malice and made Mana into a vessel, as Kitarō lures the arms to outside where Mana was located in, and shocks him with them all wrapped in his Chanchanko. Nanashi was aware of what was happening from inside himself, and summoned dark orbs to attack Kitarō and Mana, but she uses the defensive force to power up Kitarō and destroyed the orbs opening a mountain to where Nanashi's true form was hiding in. He was in the hole of the tree, and scared and angry from his hatred to the world, but summoned copies of his mask, but Mana was unfazed and began to hug him. Nanashi at first tried to resist and put on his mask, but he accepted the hug and broke the mask when Mana thanked him for being born. He felt loved for the first time in his life, since he never got the chance to be loved by his deceased parents, and Mana gave him a name. After accepting the love and name given to him, his soul peacefully fades away with a bright yellow light. His infant form shrinks and vanish, while all the damage he did to Tokyo were undone.
Archery: Nanashi appears to have am impressive skill in archery, being able to shoot an arrow from a rather far roof into the back of Kitarō.
Levitation: Nanashi constantly appears to be hovering a few feet above ground and is able to fly.
Dark Sorcery: Nanashi appears to have some connection with Jigoku as Medama-Oyaji mentioned, with many of his doings involved an inverted pentagram, such as on the arrow he used to shoot Kitarō with.
- Yōkai Awakening: He was able awaken Tantanbō, Futakuchi-Onna and Kamaitachi by placing a sheet with an inverted pentagram on the ground of a stadium, which started to glow.
- Malice Gathering: Nanashi is able to gather the malice of people and yōkai, and send it to who he desires. The negative energy is concentrated in a certain area and takes the form of a glowing red seals. The seals are the kanji of five elements; wood (木 ki) on Mana's right palm, fire (火 hi) on her forehead, earth (土 do) on her left leg, metal (金 kin) above her left eye and water (水 shuǐ) on her hair to the right.
- Yōkai Resurrection: He is also capable of resurrecting defeated yōkai, which they all possess an inverted pentagram somewhere on their face, such as the forehead or nose.
Extendable Tongue: He is shown to be able to extend his tongue to long lengths, reaching the back of a middle school student while standing straight.
Intangibility: He is able to pass through solid matter as he pleases, as shown when Mana encountered him at night by herself.
Sound Distortion: Nanashi is able to distort and alter sound, making those who he chooses to hear what he desires.
Nanashi Void (名無し虚無, lit. Nameless Void): After absorbing the energy from the five seals implanted in Mana and herself, Nanashi transforms into a giant monstrous baby. His power is so great that not even Kitarō was able so as much as scratch him no matter the attack used. Inversely, Nanashi is able to easily deal with Kitarō with mere slaps. His dreadful power is such that he is able to seemingly disintegrate his surroundings with a mere slap into the ground.
- The symbols Nanashi uses are based off of the five elements of Wu Xing: Wood, Fire, Earth, Metal and Water.
- GeGeGe no Kitarō (2018): Episode
- GeGeGe no Kitarō (2018): Episode 25
- GeGeGe no Kitarō (2018): Episode 2
- GeGeGe no Kitarō (2018): Episode 3
- GeGeGe no Kitarō (2018): Episode 11
- GeGeGe no Kitarō (2018): Episode 12
- GeGeGe no Kitarō (2018): Episode 19
- GeGeGe no Kitarō (2018): Episode 27
- GeGeGe no Kitarō (2018): Episode 37
- GeGeGe no Kitarō (2018): Episode 42
- GeGeGe no Kitarō (2018): Episode 48
- GeGeGe no Kitarō (2018): Episode 49