Katasuke Tōno

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

Background
After the Fourth Great Shinobi War, Katsuke headed up an effort to help all surviving war causalities recover from their maiming injuries. 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.

Personality
While seemingly loyal to Konoha and working to advance its prosperity, Katasuke's main goal is his own success and status. A very arrogant, immoral and self-serving man, he takes great pride in his scientific advances. Believing strongly that his work is the new era of shinobi combat, he regularly makes video journals of his work. He is also quite stubborn and self-absorbed, to the point of defying rules and orders, as even though Naruto, the Seventh Hokage, told him that he could not use the Chūnin Exams as a chance to show off his Kote, he did so anyway. Even after Boruto's disqualification in the Chūnin Exams for using the Kote, Katasuke still tried to convince the spectators of his superior ninja tools as beneficial to the village.

He is also very reckless and over-confident, as he snuck into the battle against Momoshiki Ōtsutsuki, waited until Momoshiki was down, and then swooped in for the kill, planning and hoping to steal an easy victory against the power-hungry man for further publicity of himself and of his invention--only to instead give Momoshiki extra chakra to absorb and restore his power. This move shows that for all his methodical approach to science, he is very ignorant on the battlefield, as evident by his forgetting completely about Momoshiki's ability to absorb abilities, plus not even considering the potential danger of the enemy's new form, and not listening to Naruto in the first place when he told Katasuke to not attack Momoshiki.

However, after the battle with Momoshiki, it is revealed that Katasuke's behaviour was caused due to him being controlled by someone, as Shikamaru Nara stated that Katasuke was acting weird sometime prior to the Chūnin Exams. As a result, after he's freed from being controlled, Katasuke becomes extremely shocked about his actions to the point where he was momentarily paralysed after learning about it. Once recovering from the shock and returning to his former duties, Katasuke's nature seemed very much the same in that he was eager to continue advancing his work, but also showed true concern for others, offering to help Ao when he noticed that his prosthetics were working rigidly. He also admires the earnest of experienced shinobi. He is also shown to be a very responsible person, 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 of 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.

Versus Momoshiki Arc
Unbeknownst to him, Katasuke was placed under a genjutsu by Ao to extract information for Kara. This left Katasuke more amorally ambitious in his research. Katasuke invents a forearm device that stores and releases ninjutsu at the user's will. He wanted to introduce it at the Chūnin Exams but the Seventh Hokage considered it to be a form of cheating and forbade it. However, unbeknownst to Naruto, Katasuke gives the device to Boruto to use in the Chūnin Exams, in the hopes of gaining publicity for his invention. Once Naruto discovers this and disqualifies Boruto for cheating, Katasuke tries to announce to the audience that there was no point in using traditional ninjutsu techniques due to how far advanced their technology is before Momoshiki and Kinshiki Ōtsutsuki attacked the arena. Katasuke and his assistant secretly follow the rescue mission sent to rescue Naruto from the two enemies. After Naruto and Sasuke Uchiha defeated Momoshiki, Katasuke rushed in an attempt to finish off the enemy with his device and claim the credit for the victory. However, he inadvertently restored Momoshiki's strength as the latter was able to absorb the attacks Katasuke fired at him. As a result, Katasuke was stripped of his position and was forced to do menial labour to help rebuild after Momoshiki's attack.

Mujina Bandits Arc
After being interrogated by Ibiki Morino following the battle, it's concluded that Katasuke was being controlled by someone for the duration of the exams. 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 or evil, but all depends on how it is used.

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 counted 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 find Konahamaru and Mugino in a nearby cave. They were all then confronted by Ao, aiming a machine gun at them to question them on what they learned about the black container.

Ao then unleashed a barrage of Fire Release Bullets from his gun, making everyone realising that he a scientific ninja tool. 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 Katsuke 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 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 futile 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 learned that all tools are either good of bad depending 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 him.

Trivia

 * 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.

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."