In the final story arc, Seiuchin has grown sick of Mantaro Kinniku's numerous thoughtless remarks about him and leaves the Seigi Chojin side to form the Hell Expansions with Neptuneman. Neptuneman awakens Seiuchin's ferocious animal instinct, transforming him into a blood thirsty beast. Ever since, Seiuchin has appeared as an enemy of Mantaro and the others.
Neptuneman stunned everyone by choosing mild-mannered Seiuchin as his tag partner. Neptuneman had remembered the story of The Walrus and the Carpenter from his homeland and decided to train Seiuchin to bring out the untapped cold-blooded power in him, transforming him into a violent beast. As "The Hell Expansions", the two of them are collecting the skin off of their opponent's faces instead of masks.
This was until the team faced off against the "Hell's Bears", which consisted of Belmond (Warsman) and Michael (Mammothman). Seiuchin fought Mammothman, and in the middle of the match, returned to his senses and betrays Neptuneman. However, Mammothman betrays Warsman and sides with Neptuneman, which leads to both of them knocking off Seiuchin's face with an Optical Fiber Cross Bomber and defeating Warsman.
- Optical Fiber Cross Bomber (オプティカル・ファイバー・クロスボンバー)
- Large optical fibers protrude from Neptuneman's arm and attach themselves to the opponent's back, while Seiuchin does the same from the front with one of his tusks, holding the opponent in place. They then perform an explosive Cross Bomber. The result of this technique is that the skin on the opponent's face is knocked off.
- Expansion Turbine
- Flying Walrus
- Rampage Wheel
- Hedgehog Ball
(More to Come)