As a "Gedou", a half human-Ayakashi, Akumaro could never experience Hell and was trapped within his own existence, thus his obsessive desire to bring Hell forth so he could know of its existence.
Akumaro was originally sealed away within the bottom of the Sanzu River, but the overflowing energy of Dokoku Chimatsuri gave him the energy to re-emerge from it on the surface. He appears to side with Doukoku's conquest, but secretly held his own dark desires that he kept hidden from everyone else, to open a gate to Hell so he experience it firsthand. To achieve this, Akumaro began to target several specific "points" in Japan where the Ayakashi would generate fear so it would collect in the ground. Akumaro also obtained Dayu Usukawa's shamisen and Juzo Fuwa's sword Uramasa so he could force both of them to join with him in order to get what they want back.
As the loss of Dayu and her shamisen becoming too unbearable, Dokoku emerged from the Sanzu River to take it back from Akumaro at risk of dying from rapid and severe dehydration.
It is eventually revealed that Akumaro's plan was in fact to trigger several points of weakness in Japan which would ultimately open a gate to Hell and consume Earth and the Sanzu in the process. For that ends, he also created his greatest "weapon": Juzo Fuwa and his sword Uramasa, made from the souls of his family for the purpose of having a human/Gedou hybrid who could open the Hell gate and therefore unleash the horror upon the world.
However, Akumaro's great plan also lead to his downfall: when finally giving Juzo his sword back to complete the gate, the fallen warrior slashed him with Uramasa, claiming that he knew of the souls of his family being in the sword long ago and chose to remain a Gedou to satisfy his desire to fight. With Akumaro rampaging, the Shinkengers put him down once, while his "second life" took everything that the six samurai had until a combination of all twelve of their Origami (the Samurai Ha-Oh combination armed with the Kyoryu Origami) finally put him down. In his last moments, Akumaro showed elation as he died, as he finally got the chance to see Hell in all of its glory as his body was destroyed.
- His name can be translated as "sinewy husked evil one" (筋殻の悪麿, sujigara no akumaro)
- Serrator - Power Rangers counterpart in Super Samurai.