Mutou Ryuuji is a member of the Second Karate Club and is a Kaburagi-Ryu 2nd dan (2nd level black belt within the kaburagi school of karate).
He is a tall, well-built, highly muscular young man with black hair. Light-skinned. He is so big most of his companions call/compare him to a gorilla. After a year of training with Aniya sensei, Ryuuji has grown 2-3 inches taller and his muscle tone got thicker too. Before the One year time-skip he was over 100kg (which is 220 lbs). After the time skip, he is large enough to be considered a super heavyweight.
They're dating and were rumored to be before the start of the series. Kou Haruka is so much in love with him that she traveled all the way to Okinawa when she thought he wasn't taking his training seriously. After the loss to Satomi, Mutou promises he won't return to see her until he becomes the best among men. After the two year time-skip she travels with Mutou to begin her quest to become the strongest woman.
Weighing 103kg before his fight with Satomi, Mutou was able to throw Kevin Norton out of the ring with a simple punch to the guts when Kohinata Minoru couldn't KO Kevin with his Kicks. Mutou is often compared to a gorilla by his fellow club members because of his size and strength.
He is seen eating dog treats/beef jerky and used a mask and voice-changer on a can to conceal himself and then challenges high-ranking members of the martial arts clubs (is seen fighting the head of the judo club, Tamura Keita, also seen on a warning on a notice board, implying Tamura isn't his first target) Mutou is the guy who abducts/recruit Minoru after saving him and Nana from some members of the gymnastics team who were beating up Minoru and sexually assaulting Nana. He wants to teach Minoru to be more manly, to toughen him up. Mutou finds Minoru while he is telling Nana about him joining the karate club.
While Mutou is talking with Minoru, they're interrupted by several members of the judo club, seeking revenge on Mutou after the fight with Tamura. More than seven members plan to attack Mutou, who quickly beats up two members with a single punch each. They are then interrupted by Tachiyama Yoshiaki. It is revealed that the two have fought before, where Tachiyama broke Mutou's arm, and Mutou crushed one of Tachiyamas testicles and kicked out his front teeth. In the present fight, Tachiyama quickly manages to trip and mount Mutou (as he knows his pattern already). Going in for a pin, choking Mutou, Tachiyama seems to have the upper hand, but Mutou responds with a technique designed to ruin a persons eardrums by clapping the opponent upon both ears. Tachiyama pulls his head away, releasing Mutou from the choke at the same time, leaving one hand by Mutou's collar Mutou then grabs the remaining hand, and breaks the arm with a strike to the elbow, followed by a jab to the throat Whereafter Tachiyama attempts an armbar on Mutou, but with only one arm, Mutou easily pulls his hand out of Tachiyama's grip after which Mutou uses an elbow strike to Tachiyamas face, and then threatens to crush Tachiyamas other testicle (he doesn't though). After the fight, Mutou fights and defeats the remaining attackers, knocking out more teeth.
Later that day Mutou brings Minoru to a bar where he meets the other members of the karate club. At the bar Hayama Kentarou, one of the members accidentally spill beer on Kou Haruka the (female) captain of the tae kwon do club, Though Minami Hiroki, the captain of the karate club apologizes to the tae kwon do club, the captain of the tae kwon do club is stepping on his head, due to her hatred of karate practitioners (She was dating, and dumped, by a karateka) After which Mutou offers to demonstrate some karate, Haruka (the captain of the Tae kwon do club) kicks at Mutou, but stops the kick right before hitting him, Mutou on the other hand stands completely still, claiming that if the kick was serious, he would've dodged it. They do not continue the fight, but Haruka invites him over to the tae kwon do club to settle things. Usami Shunta, a member of the tae kwon do club, who is 204 cm in height, wants to fight Mutou, Haruka says no but he continues another member of the tae kwon do club says they should just go back already, and calls Shunta stupid, which angers Shunta. Mutou then provokes him by calling Shunta a dimwit after he sees that he is easily angered by nicknames regarding his intelligence. After which Shunta kicks Mutou, and they fight. Mutou, surprised by Shuntas reach, is hit by the kick, and due to some damage he took to the left arm because of the armbar during the fight with Tachiyama, Mutou is hit several times. Shunta exclaims that he will not let Mutou snatch Haruka away from him, implying he has a crush on Haruka, which may be the actual cause for Shunta to want to fight Mutou. Despite fighting an opponent with a far superior reach than him, Mutou still manages to land several kicks to Shunta's face, after which Shunta's attacks slow down, Mutou then parries a kick from Shunta, after which he kicks Shunta in the face with a joudan mawashigeri (joudan= upper level - mawashigeri= circle kick or spin kick better known as roundhouse kick) and then follows it up with a gedan (lower level) mawashigeri to the side of Shuntas knee, damaging it and winning the fight.
The next day at practice, Haruka shows up and summons Mutou to a trial with the executive board of the hyakubukai (the martial arts club alliance/association at the university) due to his attack on Tamura Keita. Mutou doesn't show up, yet the trial decides that it is just the judo clubs personal grudge. Later Mutou teaches Minoru how to fight because of Minorus and Mamiya Seijis struggle against the kendo club and Mamiyas brother, he starts out by wanting to see how prepared to get hurt Minoru is by having him hit a makiwara ten thousand times. He then brings Minoru to another gym on the campus where Minoru is to learn how to defend himself against Haruka, since Haruka practises tae kwon do, her legs and kicks have the reach of a kendo sword. After Minoru has gotten better at defensive maneuvers Mutou tells him to hit him, since fighting is about having guts. Minoru fights Mutou, but can't get a hit in, nor can he successfully avoid getting hit himself, at this point Minoru attempts several kicks, using his background in gymnastics to help him. Since none of them lands he tries out new ways to kick, and then does a doumawashigeri, a full body spin kick, without knowing what it actually is. Mutou is surprised that he figured it out by himself, but tells him that while it's a kick that doesn't land very often, it can turn the fight completely if it does. So Minoru, Mutou and Haruka decides to help him master the technique, so Minoru will be able to successfully pull it off every time. After Minorus fight, and victory against Mamiyas brother, Minoru and Hayama must run away because the members of the kendo club doesn't want the news of their captain being beaten by a white belt to slip out, after they've run away, Mutou is seen, having showed up with a katana on his shoulder, asking "Whats up...? did you have a bad dream or something?" ... "Let's play" with his signature menacing smile. Mutou hands Mamiya (kendo club captain) the sharp katana. Mamiya attacks Mutou, who stands still, Mamiya only cuts the collar of Mutou's gi, Mutou exclaims that Mamiya too is another kendo fighter who can only use a shinai, being too scared of cutting someone to use and actual sword, after which Mutou punches Mamiya on the collarbone, knocking down Mamiya, and possibly breaking his collarbone. Later, after the promotional exam of Minoru, Mamiya and Hayama, the captain of the MMA club wants to rent the dojo, but they refuse. The MMA captain is also secretly running a business where he steals underwear and clothes from female members of the different clubs and sells it to perverts, one of his costumers buys Nanas leotard, and afterward requests some sex photos of her. The MMA captain, wearing a mask and hat, knocks out Nana with an electric rod and takes her to a forest where he intents to take nude photos of her (and possibly rape her). But it is the forest where Ibuki practices by himself, Ibuki interrupts the MMA captain before he manages to take any pictures, and he runs off. Nana becoming curious about her savior asks where he works, Mutou tells her that he works at another gym, she then goes there to find out that Ibuki is teaching kids karate But the MMA captain shows up there too (this time without hiding his identity) and challenges Ibuki to a fight, Ibuki quickly kicks him in the stomach so he pukes, the MMA captain grabs the electric rod from his bag, but Mutou shows up, and kicks the rod so the live end ends up in the MMA captains mouth, electrocuting himself.
After this incident, the gay rapist shows up, a person with a mask and the same build as Mutou is raping boys from the different athletics clubs, succesfully raping several boys, and attempting to rape Minoru too. The captain of the judo club says it is Mutou even though he himself knows that the culprit is someone who specializes in pinning techniques based on his modus operandi. Mutou is however still the main suspect, after Mutou hears about this, he is very angry and determined to find the imposter and beat him. Even going out in the middle of the night in nothing but a banana-hammock, trying to lure out the rapist, while Minoru, Mamiya and Hayama is hiding, waiting to ambush the perpetrator with bats. Mutou is again being mistaken as a pervert/rapist while he is trying to lure out the real rapist.
While lying in wait, Hayama has to pee, so he goes away, meanwhile Mamiya is quickly knocked out with a chokehold by the rapist, who then immediately attacks Minoru again, Minoru yells out and Hayama comes back, but he too is quickly knocked out. Luckily for Minoru, Mutou comes back after having found some pants and interrupts them. As they begin fighting Mutou recognizes the rapists techniques as brazilian jiu-jitsu. Mutou immediately hits the rapist, whose identity is Pedro Barbaroza, the foreign exchange student from Brazil, with a mawashigeri to the side of the head, but with almost no effect, Pedro catches Mutou's kick with his neck muscle instead, Pedro grabs Mutous leg, wanting to trip him, but Mutou uses his other leg to step from Pedros arm, kicking himself up in the air and making a backflip.
Pedro charges head-on, trying to grap and trip Mutou, who in response uses a knee kick, Pedro however blocks it and manages to trip Mutou. The campus night patrol interrupts the fight and Pedro is distracted, Mutou uses this to kick him in the head so Mutou again can get up and Pedro quickly runs off. Mutou is handed a list of all the brazilian students on campus, and then goes after a guy named Alan Gomez as he is a member of the brazilian jiu jitsu club, Mutou knocks him out with a kick with no trouble, Mutou says it isn't him, and moves on to the next guy on the list, Pedro Barbaroza. They find Pedro having just defeated and currently defiling the judo club captain Tamura, which Mutou takes a picture of, using it to blackmail Pedro into following him back to the karate dojo to continue the fight Mutou wants to settle their fight, and says the winner gets both the camera and Minoru. Pedro changes into a jiu jitsu gi, and they begin their fight, Mutou lower his center of gravity to defend against the tackles, and Mutou says that he will not hold back. Pedro starts with a head on tackle, but Mutou reaches out with an open hand, obscuring Pedros field of vision, and then elbows him across the brow. Pedro tries with another tackle, but Mutou sidesteps and punches him in the back of the head and then knees him on the nose. Pedro can't reach Mutou with a tackle since his sense of distance has been disturbed because the blood from the wound on his eyebrow is forcing him to keep one eye closed. Pedro then grabs onto Mutous collar and attempts to pull him down with him, but Mutou grabs onto Pedro's hand and breaks his arm using a outside block as a strike instead. Pedro drops down after his arm is broken, and tries to trip Mutou, using the same techniques as with Hayama earlier, but Mutou uses a gedan barai (lower downward sweeping block) to push Pedros leg away and then Mutou punches Pedro in the testicles. Mutou then threatens to punch out Pedros front teeth with an elbow, but instead he elbows the floor as Minami (the karate captain) pulls Pedro out of the way, and then also invites him to join the karate club, unbeknownst to him that Pedro is the masked rapist. This also marks the end of the conflict with the hyakubukai. Then the 2nd karate club takes a trip to Okinawa. Mutou (first member to arrive due to the fact that he left during exams) is then seen training for the Kaburagi National Championship. He srikes up the interest of Aniya Souhachi ( Legendary Karate Master/"Absolute Master of the Fist") after a sparring session which Mutou kinda loses. After he returns to Akamine's dojo to continue his training regimen. It includes Ryuuji (wearing no protective equipment) sparring with every black belt (wearing protective gear) at the dojo. The club members change every two minutes everyday for two hours, but Mutou takes no breaks. Ryuuji's strength is so overwhelming that the club members normally break down first.
- Practicing karate since middle school. Said that Satoru got Mutou serious about karate.
- Childhood friends with Satoru Ibuki (Ibuki Kengo's older brother) and more or less Minami Hiroki
- Never won in a fight/brawl against Satoru Ibuki. (Fought five times). Recalls being beaten to a pulp every time.
- Doesn't care about his academics. As he travels to Okinawa to train with Akamine Kazutora, at his/another Kaburagi branch dojo, during the time Reinan University exams are taking place.
- Admired not only by Kohinata Minoru, but also Mamiya Seji (since he saved Seji from a gang of kendo seniors and unintentionally dragged Mamiya to join the 2nd karate club)
- Occasionally seen eating jerky.
- Mutou used to have propensity for groin attacks, both in real fights and in competitions where it's not allowed; he has at least two losses in competition due to disqualification because of this.
- Signature Move: Elbow strikes-he only uses elbows when he's facing a considerable opponent. It's like his way of saying "Thank You" for being interesting in a fight. Known Victims- Tashiyama Yoshiaki, Pedro Barbosa, Kevin Norton, Jack Jules, Gerard Bertrand (four times), Satomi Masahiro (three times), Minoru Kohinata, Gerald Lopman.
- If you ask him for training, it is training from hell. (The only people he has ever personally trained were a young Ibuki Kengo and Minoru Kohinata)