|This article is about a/an episode in Choudenshi Bioman.|
Ultimate Canth's Demon Sword (最強カンスの魔剣 Saikyō Kansu no Ma Ken) is the thirtieth episode of Choudenshi Bioman. It is the appearance of the last of Gear's initial Mecha Gigan, with the squadron using a new giant system from the next episode.
In the Philippine Dub, the title of the episode changed to "Red One's Called Marriage".
Shirou becomes the fake fiance of a swordmaker's daughter in order to prevent Monster from obtaining a sword for Doctor Man's final Mecha-Gigan.
The episode begins where a blacksmith is smelting the sword to make it sharpen. Meanwhile, the Bioman are in the gas station to gas up their vehicles in fuel tank until a woman named Amiko arrives to inform Shirou about something important. Arriving the playground, Amiko informs Shirou that she wants him to become his fiance, much to the group surprise. Shirou wonders why she asks about the strange request and she replies that she needs for her father's chosen. Amiko also explains that it was a tradition to her family that whoever accepts what her father chooses to become her husband. Hikaru finally decided to solve Amiko's problem as Shingo decides to let Shirou hugs Amiko as he pushes him towards her, much to Shiro's embarassment.
At Amiko's house, the blacksmith reveals to be Amiko's father where he was finally reunited with his daughter and he wants to show to his daughter of the unique sword that he had smelted earlier and also to know who will be Amiko's upcoming husband that he had chose as he orders his bald apprentice which is Monster in his disguise human form named Mondrago. Amiko seriously tells her father that she has already engaged much to his surprise as Shirou arrives in a white formal suit and he formally bows towards her father much to Monster's shock. Both Monster and Shirou recognizes each other as enemies which Amiko tells her father that she does not like Mondrago. Her father likes Mondrago rather than Shirou as he despises about him in his formal outfit. Her father knows Japanese men has a tradition to their father to choose their daughter's upcoming husband, but turns into a disgrace due to Shirou's appearance and wants him to leave. Shirou begs him to give him a chance to prove himself which Amiko's father agreed and Monster becomes dismayed by his decisions.
At Bio Base, Peebo informs the group about Shiro's decisions while at the Neo Empire Base, Doctor Man becomes furious by the delay it is due to the sword that Amiko's father had been sharpen. Mason tells him that the sword is important to him as Doctor Man explains that the sword is a true samurai sword which is tempered with spirit of the wielder and nothing will overcome when it wields it. Farrah wants to know who's going to wield it and Doctor Man wants to know who wields it as well. He orders Monster to forge the weapon as the sword will be possess its characteristic within the weapon and Monster will be handling the sword with the mechagigan, Mantis Canth much to both Farrah and Mason's surprise. Doctor Man also explains that the mecha will be equally matched against the Bio Robo. Once he was equipped with a powerful sword the battle becomes an easy bout. Mason now informs them that the Bio Team are heading to Amiko's house as Doctor Man orders the mecha to deal with the Bio Team.
On their way to Amiko's house, the Bio Team are confronted by the Mantis Canth as it attacks them. Green2 informs the group to hide at the cave to avoid its attacks as it proceeds to get through the cave as the group are later trapped inside the cave due to the mecha's attack and it tries to attack them beneath it. Peebo saw this trouble and he is unable to contact them while Doctor Man becomes impressed after the group are trapped and Monster has to complete the forge of the sword within the hour.
Back at Amiko's house, Amiko's father was very impressed to see the long sword and Amiko prepares some tea for the both of them as Monster took it much to her scare and he puts a poison on the tea as the dog informs Shirou that the tea is poisoned. Amiko's father decided not to drink the tea until Shirou drinks the tea which he ends up being poisoned much to Amiko's father shocked by this situation. Monster now gets the sword which he attempts to deal both Amiko and her father until Shirou manages to block the sword in both of his hands despite he was in a poisoned state. Shirou knows how Monster is weak as Monster knocks Shirou down as he removes his disguise to face them. Amiko's father demands to know who he is as Monster introduces to them as from the Neo Empire Gear and stating that this sword is his. Shirou realizes that he came here for the sword and demands to know what his purpose as Monster escapes. Shiro quickly chases him as Amiko's father tells him to not allow Monster to use his sword or he will becomes evil in whoever wields it. After Shirou chases him up to the forest, Monster decides to fight him while wielding the sword as the fight ensues. Monster attempts to slash him with a sword as Shirou dodges while one of its bamboo trees are been cut off. Monster taunts him that his sword is easy to beat him and death was inminent to him. Shirou dodges most of its sword attacks until he manages to knock his sword with a kick until Monster's assistant Zyuoh came to the rescue and knocks Shirou's right arm. Zyuoh also informs Monster that Mantis Canth needs that sword he was handling as both quickly escapes while Shirou pursues them.
The Bio Team manages to escape with the help of their Bio Lasers as they continued to find Shirou. Meanwhile, Shirou fights both Monster and Zyuoh in a handicap and Zyuoh manages to knock Shirou with two blows until Monster arrives using the sword to deal against him. Monster manages to slash Shirou's white rider jacket in two slashes which Shirou notices how powerful the sword is. Monster now attacks him with the sword he's handling and tries to dodge several times as Shirou was after by them until Zyuoh hits him with Finger Missiles knocking him down through the lower stream. As they tried to finish Shirou with the sword, Yellow4 manages to rescue him as she hits Monster's right chest with a Bio Arrow and both noticed the Biomen are here much to Shirou's happiness and its rescue. Shirou angrily transforms into Red1 as the group face them. Monster orders the mechaclones to deal with them. Both Red1 and Monster clashes in a sword fight while his group fight against Zyuoh. Monster manages to knock Red1's sword as the latter avoids the sword slashes until he manages to block with both of his hands until he kicks through his leg and Red1 manages to knock him with a Bio Super Kick. He was later confronted by Mantis Canth and he was attacked by it. Zyuoh tells Monster to go throught the mecha with the sword as Red1 attempts to hit him with a Bio Laser as Zyuoh defends him and was hit by it. Zyuoh is later been defeated by the Biomen's Bio Miracle Wave. Monster manages to put the sword on the hill as the mecha takes it which the sword becomes a giant sword and Monster orders the mecha to finish them off.
By the time The Biomen summoned the Bio Dragon and forms the Bio Robo, both now clashing with each other. When Bio Robo uses the Bio Shield to avoid the sword attack, The Mantis Canth is able to slash the shield in half much to their surprise and Red1 has another option to deal with it which he blocks the blade with both of its hand and it manages to knock it off. The Bio Robo manages to defeat it with the Bio Triple Slash from its Super Maser and Doctor Man's plan of the time's reckoning becomes a failure to his cause. After the incident, Amiko thanked them as Shirou blushes after being thanked by her. Ryuta nudges at him to see Amiko's father who is happy and he apologizes for his actions and wants him to become his son in-law which Shirou refuses even he begs him to become his son in-law as Shirou quickly runs away as his group followed him as Amiko tries to stop her father from doing it as Shirou apologizes even his group towards Amiko's father.
- Shirou Gou (郷 史朗 Gō Shirō): Ryōsuke Sakamoto (阪本 良介 Sakamoto Ryōsuke)
- Shingo Takasugi (高杉 真吾 Takasugi Shingo): Naoto Ōta (太田 直人 Ōta Naoto)
- Ryuuta Nanbara (南原 竜太 Nanbara Ryūta): Akito Ōsuga (大須賀 昭人 Ōsuga Akito)
- Jun Yabuki (矢吹 ジュン Yabuki Jun): Sumiko Tanaka (田中 澄子 Tanaka Sumiko)
- Hikaru Katsuragi (桂木 ひかる Katsuragi Hikaru): Michiko Makino (牧野 美千子 Makino Michiko)
- Peebo (ピーボ Pībo, Voice): Yoshiko Ōta (太田 淑子 Ōta Yoshiko)
- Doctor Man (ドクターマン Dokutā Man): Munemaru Kōda (幸田 宗丸 Kōda Munemaru)
- Mason (メイスン Meisun): Hirohisa Nakata (中田 博久 Nakata Hirohisa)
- Farrah (ファラ Fara): Yōko Asuka (飛鳥 裕子 Asuka Yōko)
- Monster (モンスター Monsutā): Strong Kongō (ストロング金剛 Sutorongu Kongō)
- Zyuoh (ジュウオウ Jūō, Voice): Masahiro Anzai (安西 正弘 Anzai Masahiro)
- Kanemitsu Kunitomo (国友兼光 Kunitomo Kanemitsu): Gen Takasugi (高杉玄 Takasugi Gen)
- Akiko Kunitomo (国友明子 Kunitomo Akiko): Aiko Tachibana (立花愛子 Tachibana Aiko)
- When Monster attacks Shiro with his sword, Shiro is able to dodge its attacks with three reverse backflips. As it reveals that the actor has athleticism which he knows how to backflip. He is also shown to do a single reverse backflip to avoid Monster's attack before he was attacked by it.
- Shiro's second outfit has battle damage yet again after Episode 17 which Monster manages to slash his white rider jacket two times with the sword.
- Monster and Zyuoh are not seen with their mechaclones as the Biomen confront them. But after the Biomen's motto, the mechaclones appear behind them.
Choudenshi Bioman Volume 3 features episodes 22-31.