He is formerly a Seigi Chojin, which features as a main antagonist in the Chojin Ittosai of the manga Kinnikuman Nisei ~All Chojin Dai Shingeki~. In his quest for strength, he received the cursed Hell Armour from Satan which turned him evil. He has a soft spot for cats.
The Top Chojin Contest occurs at Yokohama International Stadium, between the Seigi Chojin and Akugyo Chojin.  The Doomman appears in the preliminary match, as greased-up monkey-bars appear and the chojin who can hold on the longest will be considered the victors.  The chojin start to fight amongst themselves, and Doomman attacks Jade.  He attacks with a Doom Ball, which is the perfect counter to the Red Rain of Berlin, and follows with an Armageddon Hammer. 
The next day, at a Tokyo amusement park, Doomman is announced as one of the eight finalists.  He picks the number-one ball, which allows him to pick his placement in the tournament, and he picks the A Block first-round. He is matched against Fiona.  The match takes place on the top-floor (eighth floor) of a department store.  Fiona throws her hat at Doomman, as she enters the ring.  The two engage in a series of blows, with Doomman seemingly having the upper-hand, but he soon counters with a Power-Bomb.  Fiona then takes him in a Triangle Choke Hold. 
Doomman squashes Fiona, in retaliation, with his Doom Ball against the building itself.  He then repeats his Doom Ball attack several times, until he removes her clothing with his Meteor Slicer. This causes Fiona to faint outside of the ring in a partially nude state. He leaves Fiona alone, while he laughs as he leaves the ring. 
During the semi-finals, Kevin Mask and Doomman take a train to their match.  They arrive at Tokyo Station, where the match will be a "trampoline death-match", and the match begins to a slow start, as Kevin struggles to get a proper footing on the trampoline.  Doomman takes advantage of the trampoline to increase the power of his Doom Ball.  He manages to get Kevin at a disadvantage, which allows him to gain the upper-hand.  Kevin attempts a signature move, but the canvas stops the momentum, and allows Doomman to counter with a series of blows, until Kevin attempts a Big Ben Edge.
Doomman uses a Meteor Slicer, which follows with Kevin using his Maelstrom Power.  One of the metal posts melts from Kevin's Maelstrom Power, and Doomman spreads the iron around the ring, which makes it into a metallic surface.  Kevin tries a Reverse Tower Bridge, and Doomman tries to damage his armour with a Meteor Slice, which angers him, as it was made from all the armour of his ancestors.  Doomman sends all the other iron posts of the ring flying around in the air, which he uses to attack the audience, and Kevin declares he does not care if humans get hurt.  When Doomman continues to try to hurt Kevin's armour, Kevin throws it away, declaring he will win without the armour. 
Kevin throws his armour onto broken train tracks, saving the people on the train.  This allows Doomman's Meteor Slice to pierce his flesh and force him to lose consciousness from blood loss. Doomman then returns to his dressing room, where he feeds a cat and removes his armour, revealing a magical power is what keeps it attached to his form.  The final match against Mantaro Kinniku is announced for two days later, in Aichi, Nagoya.  The ring is on top of a giant, transparent mortar, which has no canvas and only safe edges. 
Doomman starts strong with an upper-hand, getting in a series of blows and hurting Mantaro with a Dragon Suplex, which he follows with a Doom Ball.  With Okan's support, Mantaro manages to counter several of Doomman's moves.  It is revealed that Doomman obtained his powers from Satan, and - as he fights with his evil side - injures the cat he previously loved. He shreds the edges of the mat, creating a whirlpool structure around the edges of the mortar.  Doomman rolls down this structure, where he attacks with his Meteor Slice.  Doomman starts to gain the upper-hand again, but his brutality causes a member of the audience to throw a bottle at him; his cat jumps to protect him, which hits the cat. 
This brings out Doomman's humanity, as he nearly castrates the man that harmed his cat.  He nurses his cat and his armour parts from his body, and - after another flashback to his deal with Satan - Mantaro is able to gain an advantage.  This leads to an exchange of blows.  Doomman regains more of his humanity, as his cat starts to paw for him in sympathy and offer its support, and Doomman reneges on his pledge to Satan, removing the crosses of his Meteor Slicer as proof of his change of ways.  They then engage in a fair-match, which results in Mantaro nearly ending the match with his Muscle G technique. 
Ramenman prevents Ikemen Muscle from calling the end of the match, which leads to Doomman throwing away the rest of his anger and pledging himself to the Seigi Chojin, and finally Mantaro wins with a Pile Driver technique.  In the epilogue, Ramenman gives Doomman his medal for second-place and Mantaro helps him to stand when he needs support.  A month later, Doomman joins the New Generation - including those like Okan and Fiona - in new adventures and protecting the world, as a team. 
- Adds rotating blades to his Doom Ball
- Turns into a giant ball, as a perfect defence
- Bashes into his opponent with his Doom Ball
- Win/Loss Record (Single)
- O Jade (Armageddon Hammer)
- O Fiona (Meteor Slicer)
- O Kevin Mask (Meteor Slicer)
- X Mantaro Kinniku (Tombstone Piledriver)
- Laugh: Zao-zao (ザオザオ)
- Submitted by: Tomoki Isomura (磯村知起) of Tokyo as Cross Boxer.
- Doomman's homeland was changed midway from Iraq to the fictional "Zankoku"