He is known as the "Lethal Weapon" (リーサルウェポン, Rīsaruu Epon).
A 3rd dan, Doppo's adopted son and current prodigy of Shinshinkai karate. Katsumi is initially very cocky and reckless, but later matures into one of the strongest fighters in the Baki world before his battle with the prehistoric man Pickle. Nevertheless, Katsumi is an unbelievably durable person who is always seeking to better himself mentally and physically. After losing to Kaioh Retsu, he fights him to a draw in a rematch. Despite being nearly killed by Dorian, it doesn’t take long for him to seek a rematch with Dorian and return the favor of a near-death experience to the American. Also, he emerges from Doyle’s explosion burnt but ready to fight him and knock him out. Every fight for Katsumi is another chance to improve.
Katsumi and Doppo's relationship is not much like a typical father and son but more like friendly rivalry competing in the Maximum Tournament to win the champion belt for Natsue Orochi or proving who's Orochi style of Karate was superior. Nonetheless the two care about each other in their own way.
As the youngest Karate Master in the franchise he is portrayed as exuding an air of confidence and consistently wears a smug smile, believing himself to be atop the martial arts world. This is evident when ignorantly he provokes Yujiro Hanma during the in the beginning of the Pickle Wars Saga. After his fight with Pickle he matures and is often depicted as calm and composed.
Katsumi is young man of large build standing just over six feet. He has brown hair in a flap top, thick eyebrows and grey eyes. Also, his look and hairstyle often changes in the series.
Baki the GrapplerEdit
He is the adopted son of Doppo and Natsuki Orochi when Katsumi's real father was a lion tamer in a circus that both him and his dad used to work. His birth father was accidentally slaughtered by one of his circus lions. Doppo decided to adopt Katsumi, raise and trains the child as his own.
Maximum Tournament SagaEdit
He is first introduced before the Maximum Tournament, where his character is shown fighting some thugs on the street. He proceeds to beat them senseless, even going so far as to rip out one of the mens' two front teeth with just his fingers. During the Maximum Tournament arc, he knocks out the Yasha-Zaru Jr that crashes the tournament and has a small altercation with Baki Hanma. He faces Roland Istaz in his first match. Istaz tries unsuccessfully to dislocate/break Katsumi's arm, and is quickly defeated.
Katsumi's next opponent was the young yakuza leader Kaoru Hanayama, whom Katsumi had an altercation with previously in the warm-up room. Katsumi is unprepared for the strength and determination of Hanayama, and sustains extensive damage from Hanayama's attacks. After feeling hopeless and questioning his ability to fight on, Kiyosumi Katou and Atsushi Suedo rally and restore Katsumi's will to continue fighting. Katsumi is then forced to use his special technique the Mach Punch, in which Katsumi punches so fast that his fists break the sound barrier. Hanayama is defenseless against the unleashed Mach Fist and is soundly defeated. However, Katsumi sustained so much damage during the battle that he has to be carried out by his fellow Shinshinkai students Katou and Suedo.
Katsumi's final match in the tournament is against Chinese Kenpo practitioner Kaioh Retsu, who has had very little difficulty in his previous matches. Due to his extensive injuries and cocky attitude, Katsumi is defeated with one punch that sends him flying into the crowd, although Katsumi does get back into the ring only to pass out from the damage. Retsu then praises Katsumi on being able to get up after taking one of his punches. Katsumi is later seen in shock when he witnesses Baki perform the Mach Fist against Jack Hanma, and is also seen congratulating Baki after his tournament victory.
Most Evil Death Row Convicts SagaEdit
A short time after the Maximum Tournament, Katsumi has a formal rematch against Retsu Kaioh in the Shinshinkai building. The two fight to a draw, only to be interrupted by Dorian. Dorian proceeds to surprise attack Katsumi, eventually using Katsumi's own Karate belt to choke him. Katsumi retaliates, but is hit in the throat with a splintered piece of wood thrown by Dorian, who then escapes after using a fire trick against Retsu Kaiou. Dorian later crashes a meeting between Baki Hanma, Mitsunari Tokugawa, Doppo Orochi, Goki Shibukawa, Kaoru Hanayama, and Kaioh Retsu, but is taken by surprise when Katsumi shows up and attacks him. Katsumi douses Dorian with gasoline and lights him on fire. Dorian later escapes when he regurgitates a grenade and flees during the explosion.
Katsumi is seen later as Dorian is lured into an amusement park to fight the Shinshinkai Karate School in retaliation for nearly killing Kiyosumi Katou. He volunteers to fight Dorian, but is pushed aside by his adoptive father Orochi Doppo and becomes a spectator in the ensuing battle. After Dorian's defeat, he is not seen until the convict Hector Doyle infiltrates the Shinshinkai building and sets off an explosive that destroys the entire floor. Doyle is later brought back to the Shinshinkai building where Katsumi is waiting for him, although Katsumi now has burn marks all over his body with most of his hair singed away. Katsumi repeatedly attacks Doyle and renders him unconscious, but later praises Doyle after he was not afraid to take one of Katsumi's strongest attacks head-on. Katsumi arranges for Doyle to leave the country and teaches him some Shinshinkai Karate techniques. Before Katsumi departs, he gives Doyle his black belt.
Wildman War - Pickle Wars SagaEdit
Katsumi is one of the fighters that break into Pickle's living area in an attempt to test himself against the prehistoric man. He unsuccessfully tries to attack Yujiro, who humiliates him by telling him that "nobody wants to seriously fight with him". When Katsumi later hears about the defeat of Retsu Kaioh at the hands of Pickle, he tells his father that he is going to be the one to take Pickle down. He begins training hard, and even attacks Doppo to signify his newfound resolve. Retsu Kaioh later visits Katsumi while he is training, and offers to let him carry on the 4000 years of Chinese Kenpo. Katsumi refuses and makes it clear that it has to be Karate that is used to defeat Pickle. Retsu then trains with Katsumi and teaches him everything he knows, and Katsumi uses this to refine his own Karate (the 501st year of Karate). Kaioh Kaku shows up and offers to teach Katsumi a "perfect" technique, which Katsumi later crafts into a newly revised Mach Fist in which he attains ultimate relaxation and flexibility in his muscles when delivering the punches.
With his newfound strength and techniques, Katsumi arranges to fight Pickle in an arena where 55,000 Shinshinkai students have come to cheer him on. Katsumi's attacks are shown to be ineffective at first, but once Katsumi unleashes his improved Mach Fist, Pickle is brought to his knees for the first time in history. However, the aerial wall that Katsumi must break when performing the Mach Fist mangles Katsumi's hands and feet, rendering him unable to continue fighting. When Pickle prepares for his final attack, Katsumi unveils his ultimate Mach Fist technique and seemingly defeats the prehistoric warrior. The use of this final Mach Fist has a price: Katsumi's hand is reduced to bone and ligaments. Katsumi raises his arm in victory, but notices that Pickle was only sleeping and implores Pickle to finish him off. Pickle rips Katsumi's mangled arm from his body, which causes Katsumi to pass out from the blood loss. As a sign of respect, Pickle walks away and does not eat Katsumi, allowing him to be carried out on a stretcher. Katsumi is then seen recovering in a hospital having tea with Retsu Kaioh and discussing the merging of Chinese and Japanese martial arts. Baki steps in to visit and has the responsibility of fighting Pickle passed on to him by Katsumi. Katsumi is later shown practicing his new one arm techniques alone in the Shinshinkai building, until Baki shows up and has a conversation with him.
Above-Ground Great Quarrel of Father and Child SagaEdit
Katsumi is shown as one of the spectators watching Yujiro Hanma fight Baki's fighting aura at the conclusion of the Hanma Baki manga series.
Katsumi is very strong and powerful fighter. He is taller and stronger than Western. With his karate, he was strong enough to defeat Yasha-Zaru Jr with a few techniques. He also defeated Kaoru Hanayama with his Mach Punch. He could easily defeat Hector Doyle in a fight. Katsumi has amazing durability and pain tolerance: withstanding Kaoru's punch and his Vice Grip, fighting Dorian after being poked in the eyes and being choked with his Karate belt and surviving after Dorian threw a broken board into his throat, fighting Doyle after being burn by mixed wheat flour and gun powder and defeating him. He managed to withstand the pain after his fist and leg being mangled by the sound barrier from using the Mach Punch and stayed conscious after using his Hitless blow that tore all the tendons in his arm, skin and left only the bones. He even stayed alive after Pickle cut off his arm, causing massive blood loss. Despite all of that, he was once defeated by Retsu with a single punch, and he was defeated by Pickle.
During his fight against Kaoru Hanayama in the Maximum Tournament Saga, he uses a technique that was similar to the Shining Wizard move. Katsumi first strikes a kick on the yakuza boss stomach, then hits the Shining Wizard-like move on the jaw and finally, finish it with a vicious elbow strike right on his face, with the force of it could have almost ruined Hanayama's face.
- Ippon Ken
- Axe Kick - used once against Yasha-Zaru Jr, when the massive creature tried to brutally pummel his fellow Shinshinkai Karate fighter Kiyosumi Katou, during the Maximum Tournament Saga.
- Kick Killing Scissors
- Quadruple Median Line Strike - Katsumi attacks various points on the body in rapid succession. Used against Dorian and Doyle in the second series.
- Mach Punch - Katsumi aligns his joints perfectly to deliever a punch or punches that break the sound barrier. He later refines this technique using Kaku Kaiou's suggestion to imagine that his body is made of thousands of joints. Used against Hanayama in the Maximum Tournament and Pickle in the third series.
- Five Vital Points Consecutive Attacks
- Hitless Blow