Asumu

Asumu (アスム) is Hibiki's child apprentice, wanting to become a full-fledged Oni just like his master Hibiki in the taiko drum-based Hibiki Style of Ongekido.

Fictional character biography
Asumu is the only student of the Ongekido Taiko Drum Style. Before inheriting Hibiki's powers, Asumu was able to assume a form similar to Transformed Kyosuke called Transformed Asumu.

As a result of his master losing the ability to control his Oni powers, Asumu later inherits the power to become Kamen Rider Hibiki, and uses his new abilities to work together with Akira and Todoroki to ally their schools. Asumu later appears in the World of the Rider War after his reality is absorbed into it, being the only survivor of the attack of the Fangires led by Kamen Rider Saga thanks to Daiki.

After defeating Super Apollo Geist, the convergence of worlds is not stopped and the World of Hibiki and Asumu disappear. Following Decade's death, he is revived and reunited with his friends. He later helps revive Decade and then appears along with Wataru to aid Decade in the final battle with Super Shocker to repay Decade for saving his world, turning into Armed Hibiki thanks to Decade's K-Touch.

Forms
Just like the original Kamen Rider Hibiki, the current incarnation simply needs to tap his Onkaku against a solid surface, the vibrations from the fork causing his body to be engulfed in a fiery purple aura and assume his Oni form. Using his Ongekiko Kaentsuzumi buckle in conjunction with his Ongekibou Rekka drumsticks, Hibiki can execute his Ongekida attacks.

Notably, in one of his final appearances in the Rider War World, he calls out 'Henshin' while transforming alongside Wataru, making him the only Hibiki-world rider to ever do so.

Trivia

 * Asumu is based from Hibiki character Asumu Adachi.
 * He wears a deep violet kimono with crimson accents, the design of which is similar to the outfit of his namesake from the Warring States era in Kamen Rider Hibiki & The Seven Senki, but with the color scheme of the robes of the Hibiki of that era.
 * Asumu's last name hasn't been revealed by Toei.