Akira is a character who appears in the "World of Hibiki" arc of Kamen Rider Decade, serving as an alternate reality version of a character originally seen in Kamen Rider Hibiki. In this world, she is a dedicated apprentice to the Oni warrior Kamen Rider Ibuki, training in the ways of Ongekidō, the art of using sound-based combat to fight monstrous creatures known as Makamou. She is a determined and skilled student, considered one of the best in Ibuki's style. Her character is marked by a strong sense of conviction and bravery, as she is willing to defy her master's orders when she believes it is right. This is first demonstrated when she transforms into Kamen Rider Amaki without permission to join the fight against the rampaging Gyuki, driven by a desire to save her friend Asumu.

Unlike the original Akira from Kamen Rider Hibiki, who had a more troubled path and ultimately gave up being an Oni, this version achieves a more complete and celebrated transformation into the hero Kamen Rider Amaki. Her motivation is not solely about revenge or personal struggle but is tied to the future of her school and her friends. Alongside her fellow apprentice Todoroki, Akira becomes a key figure in convincing the older, more traditional masters Ibuki and Zanki to merge their three separate schools. She believes this unification is the best path forward for the next generation of Oni, showing her forward-thinking and leadership qualities. With the help of the visiting Tsukasa Kadoya, the titular Kamen Rider Decade, she and Todoroki succeed in their mission, and Akira is subsequently promoted from apprentice to a full-fledged teacher within the newly combined school.

Akira's primary relationship is with her master, Ibuki, from whom she inherits her powers and equipment. Their bond is central to her story, as she must earn his respect and convince him of a new way. She also shares a close camaraderie with Todoroki, acting as a peer and partner in their efforts to change the old ways. Her friend Asumu serves as a connection to a normal life and a source of inspiration, representing what she is fighting to protect. Her role in the story is to exemplify the theme of legacy and progress, showing how the new generation can honor tradition while also having the courage to reshape it for the better.

In terms of development, Akira moves from a student who must act in secret to a recognized and respected teacher. Her journey is one of proving her worth and vision, culminating in her formal promotion. Later, she is pulled into the larger conflict of the Rider War, where she is tragically killed by Kamen Rider Saga. However, her story has a final positive turn when she is later seen revived, along with her friends, after the events that conclude Decade's journey.

As Kamen Rider Amaki, she takes on the form of a blue Oni warrior. Her name, Amaki, translates to "Heavenly Demon". To transform, she uses a special whistle-like device called the Transformation Whistle Onteki. Her appearance is very similar to her master Ibuki, though with a lighter blue color scheme and a slightly smaller, more feminine frame. She fights using the Ongekikan Reppu, a trumpet-like weapon that can function as a gun to fire special projectiles called Oniishi. Her finisher, the Ongekisha Shippu Issen, involves attaching a mouthpiece to the Reppu to complete its trumpet mode, then inhaling deeply and blowing through it. This generates waves of wind and sound that ignite the previously fired projectiles, creating a massive, destructive wave that engulfs the target.