Katasuke Tōno

is a tokubetsu jōnin of Konohagakure's Scientific Ninja Weapons Team.

Background
After the Fourth Great Shinobi War, Katasuke headed up an effort to help all surviving war causalities recover from their maiming injuries. He would often visit and pester Naruto Uzumaki, the Seventh Hokage, for approval on various new projects, ultimately getting well-acquainted with the Hokage's family. He developed an advanced form of prosthetics that would allow people to return to normal life. One of his patients was Ao. At some point, he learned of Chamaru's injury and contacted Akita Inuzuka to tell her that he'd make the ninken a prosthetic limb. Upon doing so, the dog made a full recovery, and Akita became his assistant.

Boruto would often visit Katasuke's lab when he was feeling upset, hoping to see impressive new ninja tools to brighten his mood. Katasuke made a habit of having special edition games around for Boruto to play, and often gave him advice about life to help him feel better.

Personality
Katasuke is an eccentric and optimistic individual with prodigious intelligence and imagination. He is one of the most brilliant minds in Konoha, working tirelessly on his inventions with the Scientific Ninja Tool team. Talented a scientist as he is, he is humble enough to admit to his own limitations and likewise open to accept help from others, showing true interest to see what Amado's own talents could do for his research. This sometimes can lead him into odd situations, such as when he attempted to develop a device that could make the user intangible, and ended up running into a wall. Even in events like these, he is shown to be consistently in high spirits, always looking at things from a positive mental attitude. His grand goal in life is to modernise ninjutsu to the point that it can be beneficial and used by anyone to better everyday life. He is also shown to be an avid gamer, as he enjoys playing video games and works to complete them with a passion; he typically owns special edition games, which he lends Boruto, whom he respectfully calls "Young Lord".

Katasuke's personality was changed after an encounter with an agent of the organisation Kara. He became incredibly selfish, arrogant, and manipulative, using Boruto to test his new invention in the Chūnin Exams even when it had been explicitly forbidden by the Hokage. When his misdeeds were exposed, he was utterly remorseless, shamelessly using the opportunity to flaunt his genius to the assembled crowds. After he was interrupted by the arrival of Momoshiki Ōtsutsuki, Katasuke was shown to be vengeful and reckless, following the special team which was going to confront the invader, and attempting to finish him off himself in retaliation.

After the mission, Kara's control over him was broken and he reverted back to his normal self. He demonstrated great responsibility, eager to help his fellow Konoha-nin when the situation calls for it and deeply ashamed that, even if by genjutsu, he allowed his research to fall into enemy hands. His sense of duty also made him willing to sacrifice himself as a diversion to atone for his mistakes. Feeling such shame at how his research was perverted into such weapons of destruction, he came to regret creating it at all. However, Boruto reminded him that a tool is good or bad depending on how it is used, as Katasuke only used his inventions to protect and heal, reaffirming his faith in his research.

Appearance
Katasuke has a short crop of brown hair and brown eyes and wears a pair of glasses. In every day duties, he wears a complete white scientist suit without a forehead protector. In battle, he wears a complete standard Konoha shinobi uniform, however, rather than a standard red arm band depicting the Uzushiogakure crest, he wears white arm band depicting the Scientific Ninja Weapons Team crest.

Abilities
While his abilities are largely unknown, being a tokubetsu jōnin, it is safe to assume that Katasuke is a rather capable ninja. Katasuke is also fairly stealthy, as he was able to sneak through Sasuke's temporal portal almost unnoticed. As a member of Konoha's Scientific Ninja Weapons Team and inventor of the innovative Kote, Katasuke is a highly intelligent man. He can also be manipulative as he used Boruto Uzumaki's desire to surpass his father as a way of getting the boy to use his Kote. His intelligence was even acknowledged by Shikamaru, saying how valuable Katasuke's brilliant mind is to Konohagakure.

In terms of his ninjutsu arsenal, however, Katasuke seems to only be able to use the most basic of ninja techniques.

Byakuya Gang Arc
When the Byakuya Gang stole jewels from a highly advanced vault, Sarada Uchiha concluded that an Ice Release was involved in the theft. Boruto brought the new Team 7 to Katasuke for his expertise, and he in turn brought them to a black market in the village, where all kinds of questionable dealings were commonly held. There, they learned that the Byakuya Gang was going to make a trade for the jewels soon. Katasuke was eagerly inspecting all the potential new equipment he could acquire as the team departed.

Later, Katasuke was attacked by the Byakuya Gang, having engineered a riot targeting the Kaminarimon Company as a diversion. They stole a special storage unit containing all his intel on ninjutsu, what he described as his magnum opus. Before passing out, he slipped a homing beacon on Gekkō. When found by Boruto, Katasuke gave the genin the tracking system to find the thieves. Ultimately, the Byakuya Gang was captured and Katasuke regained his stolen goods, delighted to see how valuable his work really was. It served as further confirmation to his belief that his work could change the world. He opened the storage unit to reveal that the prototype Kote was also inside.

Versus Momoshiki Arc
Boruto continued to come to Katasuke periodically for advice and to vent his frustrations. Katasuke usually supported him, offering him kind words and praise. At the same time, Katasuke completed work on the Kote, which he demonstrated to the Hokage personally. He asked for Scientific Ninja Tools to be allowed in the upcoming Chūnin Exams, which the Hokage denied. Disappointed, he returned to his laboratory to consider further options. In a moment of vulnerability, he was ambushed by Koji Kashin, who placed him under the control of Kara. This experience corrupted Katasuke's morality and led him to exploit his friendship with Boruto in order to perform illicit field tests of his new device in the Chūnin Exams against the Hokage's wishes. One of his agents kept him informed of events as they proceeded, and Katasuke was delighted to hear his device had been used by Boruto to advance. He even personally congratulated Boruto after one victory, saying they would change the world, and providing a special capsule for the Kote. This capsule contained Lightning Release: Purple Electricity, which Boruto would use in desperation in his battle with Shinki, ensuring victory.

However, the advanced nature of the technique led Naruto to realise what was happening. He disqualified Boruto and disavowed the device. Katasuke stormed the arena and openly promoted the device as the next evolution in ninjutsu, mocking Boruto. He was interrupted by the appearance of Momoshiki and Kinshiki Ōtsutsuki in the sky above the arena and their subsequent assault on the village. Afterwards, Katasuke and his assistant secretly followed the rescue team sent to recover the captured Naruto from the Ōtsutsuki. After the team defeated Momoshiki, Katasuke tried to use the Kote to finish him off. However, he inadvertently restored Momoshiki's strength as the latter was able to absorb the attacks Katasuke fired at him. He was incapacitated moments later, but survived. After Boruto killed Momoshiki, Naruto took Katasuke into custody for his actions.

Mujina Bandits Arc
After being interrogated by Ibiki Morino following the battle, Ino Yamanaka used her jutsu on him over and over to delve deep inside his mind and Kara's control over Katasuke was discovered and broken. Upon being freed from their control, Katasuke was in shock from his actions. Shikamaru stated that once Katasuke recovered, he would reinstate his position in the Scientific Ninja Weapons Team.

Ao Arc
Sometime later, realising the presence of a looming danger not unlike the Ōtsutsuki, Naruto had Katasuke begin development of a new ninja tool based off of Momoshiki's Rinnegan power, allowing the user to absorb enemy ninjutsu. However, it was still only in the prototype state, and was not able to use Momoshiki's secondary power of replicating any technique absorbed. After the initial test on the absorption capabilities proved a success, Katasuke was to be sent back to Ryūtan City to continue development. He was assigned Team Konohamaru as an escort. While Boruto was openly against the whole thing, once on the mission, they met Ao. While Katasuke made some adjustments to the retired Kiri-ninja's prosthetics, Ao's own experience with war and advanced tech helped Boruto understand that tools are neither inherently good nor evil; it is the way in which they are used that matters.

Upon arriving at the lab, Katasuke had his escorts aid him in testing some new tools. Later, words is received that Konohamaru is missing. Boruto's team is assigned to find him, starting at the jōnin's last location. Katasuke decides to go with the genin and Chamaru, equipped with a new prototype battle armour. Arriving at the location, a crashed blimp, as they find several puppets laying about it. As Katasuke begins investigating the inside, he is surprised at the sight of a black container, recognising it. Before he could ponder more, the puppets became activated, revealing themselves to be advanced robotic tech that were highly resilient to ninjutsu. Katasuke countered the problem with his suit, making all the puppets attack him, absorbing all their attacks in a continuous pattern until the puppets overheated and shut down. As the group removed the power source, Katasuke sadly concluded that these puppets were built from his stolen tech designs. Chamaru then lead the group to Konohamaru through his sent. They eventually found Konohamaru and Mugino in a nearby cave. They were all then confronted by Ao, who aimed a gatling gun at them to question them on what they learned about the black container.

Ao then unleashed a barrage of Fire Release Bullets from the weapon. Konohamaru, with help from Katsuke, was able to destroy Ao's gun. As Konohamaru asked if this had anything to do with the organisation Kara, Ao unleashed a hidden weapon from his prosthetic shoulder, blasting Konohamaru. He then attacked Katasuke and stole one of his technique-absorbing gauntlets. After testing it himself on Boruto's Rasengan, Ao concluded that now they had to die to keep the organisation's existence a secret. Mugino then held Ao down long enough to collapse the cave on him and Ao to save his allies. His sacrifice, however, turned out to be a futile gesture as Ao quickly clawed his way out of the rubble, prompting Boruto and his team to retreat. As they took shelter, Katsuke admitted to his shame that the enemies' access to advanced ninja tech was because they brainwashed him into giving up his research. As Konohamaru insisted that they had to return the data he found on the blimp to Konohagakure, Katasuke offered to act as a divergence to atone for his mistakes. Boruto, realising that the scientist was ashamed of his inventions, reminded Katasuke that he too hated such tools at first, but that the good of all tools depend on how they are used, such as how Katasuke used his technology to help Chamaru walk again. Boruto insisted to help Katasuke stop Ao before he continues to abuse the technology that Katasuke gave Kara.

As Katasuke began explaining the nature behind the gauntlet's chakra-absorbing ability, a plan was devised around exploiting Ao's reliance on the ninja tech. Boruto was given a chakra-sword, but was warned that as a prototype, it has a serious flaw of quickly draining one's chakra reserves once activated. Katasuke then watched in amazement as Team Konohamaru was able to outsmart Ao and overpower him by exploiting the chakra-sword's key weakness, tricking Ao into using it himself. As the team surrounded the seemingly defeated foe, Konohamaru was knocked out by a bunch of Mirror Drones, blocking the attacks on Boruto with is body. Katasuke deduced the nature of the drones, concluding that they were powered through a wireless connection to Ao's chakra. Boruto held off the drone's assault with his gauntlet while Sarada and Mitsuki got Konohamaru and Katasuke to safety. Ultimately, Boruto's shadow clone deception was able to again outsmart Ao and give him the opening to strike down the foe. Moments afterwards, a mysterious man appeared and killed Ao with his Boiler Toad. He then calmly introduced himself as Koji Kashin.

As Konohamaru calmly revealed what he already knew about Koji's organisation, Koji quickly decided to destroy the Konoha-nin. Konohamaru engaged the mysterious foe and attempted to finish him off with his Rasengan, only for the man to counter technique with his own usage of said technique. While seemingly equal to each other, Koji had planted a small toad on Konohamaru, detonating and engulfing Konohamaru in powerful flames. Desperate to save his sensei, Boruto unknowingly activated the seal on his hand, which as it spread up Boruto's arm, absorbed the flames to save Konohamaru, amazing Katsuke. Impressed with the display from Boruto, Koji decided to part ways for now.

Kawaki Arc
On the group's way back to Konoha, they discovered destroyed puppets alongside an unconscious boy. As they began to examine the boy, Kawaki, for injuries, they discovered that he had a matching seal to Boruto's on his left palm. As Boruto's seal began to hurt Kawaki, also felt the pain, making him abruptly wake up and destroy the area within his vicinity. Questioning who the team were, Konohamaru identified himself, and asked for information regarding the crash. Refusing to provide information and wanting to be left alone, Boruto revealed to the boy his mark, resulting in Kawaki believing they were pursuers from Kara. As they tried to correct him, Garō made his presence known, announcing his intentions of recovering Kawaki. Kawaki resisted, showing the ability to manipulate his body structure into weapons. As Garō continued to dodge Kawaki's assault, the boy gradually exhausted himself until Garō finally attacked and pummelled him into submission.

Suddenly, Boruto's Kāma activated again, causing Boruto agony. At the same time, Kawaki's own Kāma activated, giving him newfound energy and proceeded to kill Garō with a massive blast. As Boruto protected everyone from the blast through his mark's power of absorption, Kawaki turned his attention to the Konoha team, now surer than ever that they were with Kara. The boy then proceeded to faint as his mark deactivated. Katasuke took a quick look at the boy and determined that Kawaki was an unprecedented advancement in scientific ninja tools, as his entire being was remodelled, down to his blood vessels and nervous systems. From Katasuke's analysis, it was decided to bring this boy back to meet with the Seventh Hokage.

Once the team brought Kawaki back to the village, Katasuke did a through analysis on the boy's unique body. He determined that Kawaki's body was augmented at a cellular level to instantly allow him rapid tissue change. Katsuke then brought his findings to the Kage Summit. While the Kage questioned how best to handle the boy, it was ultimately decided to treat the boy with sympathy as they were no strangers to children being made into weapons (i.e. jinchūriki). It was also agreed for the boy to live with Naruto, who would watch over him at all times.

Later, after Kawaki's right arm was destroyed by Delta, he was taken to Katasuke to repair his arm. When Katasuke informed Naruto the technology in Kawaki's body was too advanced for him to handle, Naruto found an alternate solution. The Hokage gave Kawaki one of his prosthetic arms and channelled some of his chakra into Kawaki to make it work, greatly impressing Katasuke with the ingenuity of his solution.

Later, when Konohagakure was attacked by Jigen, leader of Kara, the village was put on high alert. After a daring rescue by Team 7 to successfully rescue the Hokage, they were brought to the hospital for treatment. This included the newest resident of Konoha, Kawaki, who was of great importance to Kara. While Katasuke and Sumire ran tests on Kawaki, they determined there was an incompatibility between his prosthetic hand and his highly modified physiology, which caused him pain. Katasuke regretted not having a better grasp of the technology to help Kawaki.

When Amado from Kara sought to defect to Konoha, willing to share his intel with them, Katasuke watched his interrogation, and marvelled at the possibility of seeing his work on the lab. As he heard the truth behind the Ōtsutsuki, he was amazed to hear about their methods of transcending death by using their Kāma to rewrite people into perfect copies of themselves. Part of Amado's asylum agreement with Konoha involves him only being allowed to use their research facilities under Katasuke's supervision, and sharing with him all the information about his research. When Amado pointed out Isshiki would likely target Kawaki to reapply Kāma, Katasuke was terrified of what he would do to the village.

As Naruto and Sasuke went to hold off the sudden arrival of Isshiki, Katasuke joined the rest of the group in a special bunker with seals that would protect them for the time being. When they learned that Boruto was fighting Isshiki alongside Naruto and Sasuke, Katasuke was worried about him. Amado noted that while he was no match directly for Isshiki, Boruto's potential value against Isshiki was in another capacity.

Amado explained that Boruto, as a wielder of a Kāma, was essential to Isshiki's plans. He explained that the God Tree could only reach full maturity by sacrificing an Ōtsutsuki. This meant that with Boruto alive and once fully transforming into Ōtsutsuki himself, Isshiki could sacrifice him instead of himself. While Katasuke was horrified at this news, he agreed that for now, they had to play things out to the best of their abilities.

As Amado was intrigued by Kawaki's prosthetic arm, Katasuke noted that it was powered by Naruto's own chakra. Suddenly, a dark energy appeared. It enveloped Kawaki and he disappeared, much to Katasuke's horror.

Trivia

 * Katasuke's goal of using ninjutsu to allow anyone to use it to better their everyday lives aligns with the ideals of Ninshū.
 * A parallel is drawn between Katasuke and Mizuki in that they both tricked the sons of the Hokage into doing something risky for their own ambitions at the start of the series.
 * In the movie version, Katasuke was not noted to be under genjutsu, and was instead demoted upon Momoshiki's defeat, where he was last seen doing hard labour in rebuilding the damaged village. Also in the movie, he is ranked a normal jōnin.
 * According to character trivia from Boruto: Naruto Next Generations:
 * Katasuke's hobbies include playing one-on-one fighting games and the Extreme: Shinobi Picture Scrolls trading cards.
 * His favourite food is wonton noodles.
 * His least favourite food is little crunchy sardines.
 * His attributes are: 60 in strength, 154 in intelligence, 122 in perception, 100 in dexterity, 55 in chakra, and 130 in negotiation.
 * He was also given a skill rating in these particular areas:
 * Science: ★★★★☆
 * Art of Conversation: ★★★★☆
 * Intelligence Gathering: ★★☆☆☆

Quotes

 * (Quoted on his plaque) "Science is the pursuit of all knowledge. A scientist must, by that very same pursuit, exist for the sake of being a support for all of the people."