Born into a prestigious family, it was decided that he would follow his father's footsteps with his life was all devoted to studies, devoid of anime and hobbies. This continued until he was 7 years old when he met Toru, a boy of the same age as him, who brought him into the world of Gunpla Battles. Eventually, he was engrossed into Gunpla and became a proficient builder and fighter while constructing his first customized Gunpla; the ν Gundam Brave.
Sometime after being introduced to Gunpla, he was pressured into going abroad to study before inheriting his step-father's company. While studying in London, he was prohibited from building or playing Gunpla. At first he was resentful at all the pressure being mounted onto him but his love for Gunpla and the freedom that came with it was rekindled when he met Sei's father, Takeshi Iori.
7th World Tournament
Ten years later, when he was a 12th-grader, he became president of both Seiho Academy's student government and its modeling club. He was also adored by the student population and was extremely talented at Gunpla building and battle; making it all the way to the world championships of the last Gunpla Battle tournament. He was famously known as "The Crimson Comet"(紅彗星 Kurenai Suisei) as his second Gunpla, the RX-93-ν2V Hi-v Gundam Vrabe, can turn red when fighting. He later switched to the MS-06R-AB Zaku Amazing.
One day, he visited Sei Iori's classroom to ask him to visit the modeling club room during lunch time. Tatsuya asked Sei about how he defeated Susumu Sazaki. Sei tells him that he was able to defeat him thanks to Reiji, but Sei also says that Reiji is not interested in Gunpla battles, so he gave up on him. Hearing about Reiji increased Tatsuya's curiosity over him. Then China Kousaka enters the room, telling Sei that there is trouble, where she points outside, showing Reiji doing a wrestling move on Monta Gonda. After Sei stopping him, Monta asks Tatsuya why he is allowing Reiji to enter the school grounds, where Tatsuya lies to him saying he invited Reiji to the school for his piloting abilities, and how he was the one who defeated Susumu. Monta asks Tatsuya if Reiji can show his abilities, and that he would like to Gunpla battle against him. Tatsuya allows it, where afterwards he becomes the judge of the Gunpla battle between Sei and Reiji's GAT-X105B Build Strike Gundam and Monta's MRC-F20 SUMO. During the battle, after seeing Reiji's unique piloting abilities, he becomes fired up. After Reiji defeats Monta, he enters the battle with his MS-06R-AB Zaku Amazing, raising up his hair while saying that since the battle ended fast, it would be a shame for the audiences that have gathered. He thanks and apologizes to Sei and Reiji, where he apologizes for abruptly entering the battle and thanks them for giving him the chance to fight against them. Despite Reiji's high performance movements, Tatsuya is able to outpower Reiji and his Build Strike Gundam within a short amount of time. He stops the battle after putting his Zaku Amazing's Heat Nata against the Build Strike Gundam's neck, saying that after looking at the unit's performance and design, that it seems it is still incomplete. Sei asks Tatsuya why he is approaching Sei so much, where Tatsuya tells him that he will give him the answer if Sei can win against him, and the best place to do that is the Championship. Later after the battle, it is shown that one of the Zaku Amazing's Heat Nata is damaged from the Build Strike Gundam's attacks. Afterwards, Sei realizes that Tatsuya fought Reiji to fire up his fighting spirit for Gunpla Battles.
Tatsuya is seen monitored the school grounds with Monta, where he saw that Sei ws busy designing the Build Strike Gundam's new equipment. Later when China visits the stadium for the Gunpla Battle Championship out of curiosity, it is shown that Tatsuya and his Zaku Amazing are battling against an opponent's ZGMF-1000/A1 Gunner ZAKU Warrior. Tatsuya comments that it's a well made Gunner Zaku Warrior and that he doesn't really want to damage it, where he then shoots down the scope of its M1500 "Orthros" beam cannon, then puts his Zaku Amazing's Heat Nata against the Gunner Zaku Warrior's neck, making the opponent surrender. Tatsuya becomes frustrated and unsatisfied, asking himself if he is being arrogant to wish for a true battle. He then sees China in the audience and greets her, asking her if she was interested in Gunpla Battles. She tells him it isn't like that, where Tatsuya asks her if she came to cheer for Sei instead, as his match is coming up. After China sees a RX-79BD-1 Blue Destiny Unit 1 getting destroyed by a RX-79BD-3 Blue Destiny Unit 3 in a match in front of them, she asks Tatsuya why people are fighting with their Gunpla despite them having worked hard on building them. Tatsuya tells her it's because they worked hard on them, and that they want to prove that their Gunpla is the strongest, even if it damages their unit. Then they see Sei entering the match ground, but sees that Reiji is not with him, and wonders if Sei is trying to fight alone since his piloting skills aren't good. After Reiji appears and Sei shows him the newly built GAT-X105B/FP Build Strike Gundam Full Package, Tatsuya becomes surprised by its completeness. After the Build Strike Gundam Full Package's outstanding performance, Tatsuya becomes fascinated by its performance and fires him up.
However, he later bows out of the World Tournament qualifying rounds before his scheduled match with Susumu Sazaki. He later confronts Sei and Reiji, and they have a final match between his Zaku Amazing and the Build Strike Full Package, in which he narrowly defeats the Build Strike, though both machines are destroyed.
Tatsuya is shown to have some connection to Plavsky Particle System Engineering (PPSE) , who provide him with his next Gunpla, the PPMS-1M Kämpfer Amazing. At this time, he also adopts the pseudonym "Master Kawaguchi", donning a long, dark blue coat and sunglasses. The exact nature of this connection has yet to be explained.
Kawaguchi would proceed to demonstrate just how effective his Kämpfer Amazing would be in his great level of skill, easily shooting down his opponents during the fight with little effort. Sei and Reiji noticed his similarities to Tatsuya, and promptly confronted him about it. Kawaguchi disregarded the accusation, while very suspiciously saying information about Tatsuya he shouldn't be supposed to know. Even after showing his real face and clearly demonstrating he was indeed Tatsuya, he continued to disregard their accusations.
Tatsuya would later show that his alter-ego was a stressful job, but nonetheless continued to act like him during the Tournament.
During the Battle Royale, Kawaguchi easily overpowered his opponents while clearly having the disadvantage in numbers, shooting down two attackers with his Kämpfer Amazing's combat knives and shooting the rest down with the rifle. Later on, he witnessed a gigantic MS-06 Zaku II emerge from the wreckage of a recently destroyed Gaw. Kawaguchi dashed towards the fighting field in order to assist Sei Iori and his allies in defeating the computer-generated Gunpla, but his manager convinced him to stay out of the fight.
Nonetheless, he still provided assistance by using the Kämpfer Amazing's sniper rifle to fire on the Zaku's leg and knock the Gunpla off balance, allowing Reiji to obliterate it.
Kawaguchi was clearly angered at the intervention from the Chairman Mashita, personally going to his lounge to confront him about it. While Mashita was laid back about the situation and using the excuse of boosting TV ranks, Kawaguchi seized his wrist and applied pressure into it, all the while stating his displeasure with the addition of a computer-generated Gunpla as well as demanding such action not to be done again before taking his departure.
Further into the Championship, each contestant was ordered to draw out numbers for specific weapons, himself drawing out Weapon 01. In the battle, he discovered that the weapons assigned were a pair of Tonfas, while his enemy had received a railgun, but lacked knowledge in how to utilize it. Kawaguchi showed his impressive skills once more and swiftly defeated his foe's Gunpla, stating that a powerful weapon was not useful without proper usage.
Kawaguchi moved forward easily to the finals of the World Tournament, where he faced the Renato Brothers and their GM Sniper K9. With their ingenious use of traps and the K9 Pack, Meijin and Allan were forced to hide inside an abandoned stadium, by which point the Brothers put to use their secret weapon: eight 1/144 Zeon Soldier figures, nicknamed Bloodhounds, who proceeded to plant time bombs in the Kampfer's joints. However, Kawaguchi evaded defeat thanks to pre-applying grease to the joints, thus avoiding destruction of his unit. Even after the brothers activated the EXAM System, Kawaguchi managed to turn the tables on both of them using wit and strategy of his own, though the Kampfer sustained atrocious damage in the end, to which Yuuki declared he failed as a Meijin.
In order to keep fighting in the tournaments, Allan Adams requested that the Exia Amazing be sent for the Meijin's use, even though it was incomplete. As he evaluated his new Gunpla, Kawaguchi and Allan discovered his next opponent was changed: he would instead fight Julian Ayers Mackenzie, his old Gunpla Academy coleague. He also declares to Allan that the following day, they might lose.
In the semi-finals match, both Julian and Kawaguchi fought evenly, with the Meijin managing to evade Julian's Gundam F91 Imagine attacks and even its Back Jet Stream, which gave the Gunpla tremendous speed. In the middle of the fight, Kawaguchi declared to Allan that he would forfeit his title of Meijin for this fight, instead taking up his real name, Tatsuya Yuuki, claiming that if he defeated Julian as himself, then he would become the Meijin he truly aspired to be. After a grueling battle, in which Julian almost defeated them with the mouth-mounted beam cannon (which he only managed to avoid thanks to his sunglasses, which protected his eyes from the blinding flash), Kawaguchi won the fight utilizing Trans-Am (a risky maneuver, since Allan later mentioned that the system was only partially complete), advancing to the finals to fight Sei and Reiji.
After the semi-finals, he also visited the second Meijin, an man bed-ridden in the hospital, and linked to several machines (theorized to be life support units), stating that he now became the third Meijin, but would not take up the second's ideology of building Gunpla only for victory, but instead would uphold the ideology of the first Meijin, building Gunpla for fun and pleasure.
Later, during the Gunpla Eve, Tatsuya discarded his Meijin persona and went to the festival as himself, in which he met Sei and Reiji. The three walked away from the festival and talked about why Yuuki bowed out of the Battle Championship, and also reveals that his passion of Gunpla came from Takeshi Iori, Sei's father, who taught him that Gunpla means freedom. All three agreed to have a final showdown on the next week, to finish their battle once and for all.
In the day before the final match, Yuuki and Allan were reviewing the completed Exia Amazing, when Mashita walked in with four bodyguards. The Chairman said that Kawaguchi had to win, for if he lost, then PPSE would have funded him for nothing. Tatsuya says he will do his best, but Mashita says he simply cannot lose, and instead lectures him into attacking his enemy on the weak spot continuously, without showing mercy, to which Yuuki realizes it was Mashita's fault that the second Meijin became the "demon" he was known for. Refusing to fight in such ways, Yuuki and Allan were restrained by Mashita's bodyguards, and saw Nine Barthes enter the room with the a special headgear containing the upgraded Embody System. Mashita and Barthes then forced Yuuki to wear the headgear, and allowed the Chairman to exert his will (victory at all costs) into Yuuki, turning him into a person akin to the second Meijin.
During the finals, Yuuki displayed uncanny cruelty and savagery, repeatedly attacking the Star Build Strike Gundam, though only aiming for its joints. Mid-way through the fight, after destroying the Strike's rifle, shield and booster, the field was changed into a single metal corridor, thanks to intervention from Baker, and managed to pin down the Star Build Strike to a wall with his Exia Dark Matter's Prominence Sword and ripping off its head vulcans. However, Sei and Reiji managed to tip the odds in their favor, ejecting the Build Strike's right arm and damaging the Dark Matter, in the process acquiring its Prominence Blade. After engaging Trans-Am, the field was changed yet again to space by Baker's orders, and Mashita tried to order Barthes to increase the Embody System's output, but this plan failed (due to Allan Adams's intervention, who was being kept inside the same room as Barthes, and tackled him down to prevent the manager from utilizing the system). Kawaguchi attempted to use the Dark Matter Booster against the Star Build, but Sei and Reiji manipulated the Discharge System to fire the Prominence Blade as a projectile, destroying the booster unit. After retrieving their right arm, Sei and Reiji proceeded to use the Double Build Knuckle to destroy the Exia Dark Matter, in the process destroying the Embody System and freeing Yuuki from the mind-control. As the boys rushed to his side, he apologized for ruining the battle, but both shrugged it off and invited him to battle with them again. When Reiji asked who manipulated him, Yuuki looked at Mashita's viewing area seriously, accusing the chairman for his state. He was present when the underground Arista reacted with Mashita's own and subsequently materialized a full-scale physical replica of A Baoa Qu.
While the other Gunpla Fighters set off to stop the Arista and the army of Mocks, Yuuki wanted to help as well but couldn't as his Amazing Exia was too damaged, just then Allan arrives with a repair kit. After making makeshift repairs to the Amazing Exia, Yuuki then joins the battle against the Mocks and uses the Trans-Am to destroy a large number of them. After the Arista was destroyed, Yuuki has another Gunpla Battle against Sei and Reiji before the Gunplas fully cease to function, both sides put a decent fight but before either side could strike a finishing blow their Gunplas become inactive as their was no more Plavsky Particles left.
As Meijin Kawaguchi, Tatsuya has continuously participated in several world tournaments that followed. He has won 3 world championships in a row. At some point in his career, he has entered the Gunpla battle's Hall of Fame. He has also been a trademark figure in several gunpla events, including the Artistic Gunpla contest and Meijin Cup building contest. Aside from participating in gunpla battles, he's been roaming around gunpla battle scenes to watch and observe different fighters.
All-Japan Under-19 Gunpla Battle Championship
Seven years after the 7th World tournament, he presented Yuuma Kousaka with the the trophy for the "Artistic Gunpla" building contest. He gains an interest in Team Try Fighters as they are coached by Mr. Ral, the Blue Giant, and is often seen with Lady Kawaguchi, the only known woman to have inherited the title of Meijin Kawaguchi. He later observed Team Try Fighter's battle against Team G-Master and wants both team's Gunpla to blaze on during the heat of the battle. At the Nielsen Labs, he barged in Saga Adou's battle with the Team Try Fighter using his PF-78-3A Gundam Amazing Red Warrior. The battle was later stopped by Allan Adams. He also encouraged Yuuma Kousaka to work harder after his lost to Adou. He then continues to watch over the national championship as it progresses.
- Embody System
- Produced by the Flana Institute, it is an improved version of the Embody System used in Aila's control suit, and is mounted in a special headgear. In addition, unlike the one used by Aila, this version can resonate with the giant Arista crystal used by PPSE and with Chairman Mashita's Arista, allowing the Chairman to force his will onto the Meijin. This causes the Meijin to fight for victory and nothing else.
|“||Mr. Takeshi told me that... Gunpla is freedom. You can build it as you like. You can fight with it as you like. Just build Gunpla as you think best, and enjoy the battles to your heart's content.||”|
- He is similar to Char Aznable from Mobile Suit Gundam, and both don a mask and pilots a red mobile suit. In addition, his title "The Crimson Comet" is a reference to both Char's title as the "Red Comet" and Johnny Ridden's title as "The Crimson Lightning".
- He also performs Char's signature Red Comet Kick in episode 6, with his Zaku Amazing against the Build Strike Gundam Full Package and later in episode 24 against Star Build Strike with the Exia Dark Matter.
- His alter ego, Meijin Kawaguchi, is homage to real life person Katsumi Kawaguchi of the Bandai Hobby products department, also known as Meijin Kawaguchi and is considered as the most famous person in the world of Gunpla.
- As Meijin Kawaguchi, he has a flamboyant and over-the-top personality.
- When he pilots, he sweeps his hair up similar to Allelujah Haptism from Gundam 00 when he turned into a true super soldier.
- At the final tournament, he dressed in a different costume rather than his other costume, Tatsuya was wearing a dark long purple scheme scarf that is reference to Setsuna F. Seiei from Gundam 00.
- The Exia Dark Matter is the only Gunpla he has used that does not contain "Amazing" or "Vrabe" in its name.
- Kawaguchi was homaged in the video game New Hyperdimension Neptunia VII, where one of the users of Chirper (the game universe's equivalent to Twitter) is Meijin Takanashi the 3rd, whose design is a color-swapped version of Kawaguchi with purple hair, a white coat, and red sunglasses.
- As part of the Gundam Game 30th Anniversary Collaboration project, Tatsuya, as Meijin Kawaguchi, made his debut in video games as the initial pilot of BN-876-2H Hot Scramble Gundam.