Sea Fist Demon Rageku is one of the three original masters of Rinjuken Akugata and a major antagonist in Juuken Sentai Gekiranger.
She is grand master of the Confrontation Beast Jelly-Fist, a style that allows its user to let opponents' physical attacks pass right through, neutralizing them. Her training is based on jealousy and envy, targeting Master Sha-Fu, whom she refers to as "Darling" as he spurred her romantic feelings for him in the past. She addresses other people of lower status using the informal "-chan" suffix, as opposed to "-san".
Juuken Sentai Gekiranger
Rageku is the second of the Fist Demons to be revived, with Mele's help, buried at the bottom of the deep-sea beyond light and sound. She instructs both Rio and Mele, teaching them to use their envy to become much more powerful. Both she and Kata intended to celebrate their student's victory over the Gekirangers' defeat by destroying the city, until they sensed Rio's defeat by Super GekiRed. Rageku vainly pleaded with the enraged Rio not to revive Maku, who beats her and Kata up after his rebirth.
During the Beast Origin Village incident, Rageku uses her power to send the Gekirangers, Rio, and Mele back into the Edo era before incinerating the area in an attempt to destroy SaiDain. She later battled GekiChopper and was nearly killed by him after he managed to overcome her defenses. Though she evaded death at the hands of the Gekirangers, she is eventually murdered by Long as Maku battles the Gekirangers; turned into a puddle of her former self upon realizing Long's true nature as he takes her broken staff as proof of her demise. Her Confrontation Ki is transferred to Retsu by Rio, who utilizes it to merge her style with his own, unifying the two schools.
Super Hero Taisen
She is revived as a member of Dai-Zangyack. She is seen fighting Kamen Rider Fourze in the charge, V3 in the first aerial scene, and BoukenBlack and ShinkenRed in the second. She was last seen fighting Ax Den-O and Gun Den-O when the Den-O's and Gekirangers are fighting the Genjuken and the Imagins.
Super Hero Taisen Z
Rageku was part of an Army of Resurrected (mostly Super Sentai) monsters led by Space Raider after the revival of the Madou Demon King Psycho. They proceeded to attack the gathering of Kamen Riders and Super Sentai, giving them a hard time. The heroes of recent years were in a pinch until the arrival of a force of Sentai and Rider reinforcements led by Akarenger and Kamen Rider Ichigo. The combined forces of superheroes were able to turn the tide against the Madou army. She was seen fighting Yellow Buster and ShinkenPink. They lined up and used their various finisher attacks to destroy the revived monsters.
- She's the Super Sentai counterpart of Jellica from Power Rangers Jungle Fury.