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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 disappears. 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.

Later appearances
Movie War 2010 currently remains the last appearance of Asumu. The Hibiki that appears in OOO, Den-O, All Riders: Let's Go Kamen Riders and Kamen Rider × Super Sentai: Super Hero Taisen is the original Hibiki, Hitoshi Hidaka.

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 World of Rider War, he calls out 'Henshin' while transforming alongside Wataru, making him the only World of Hibiki rider to ever do so.

Transformed Asumu
Before inheriting Hibiki's powers Asumu was able to assume a form similar to Transformed Kyosuke called Transformed Asumu (アスム変身体), only shorter, muscular, silver and has no "mask".

Oni

 * Height: 222cm
 * Weight: 156kg
 * Punching Power: 20t
 * Kicking Power: 40t
 * Maximum Jump Height: 75m
 * Maximum Running Speed: 100m/3s

In this form, Hibiki is a purple demon. This is his basic form and the easiest form for him to reach. To become this form, Hibiki simply needs to tap his tuning fork against a solid surface, the vibrations from the fork causing his body to be engulfed in a fiery purple aura. Hibiki also gains a second "oni face" which is a crest that forms on his forehead. Unlike most Kamen Riders, Hibiki does not wear a suit, rather his demon form is his true form.

Armed

 * Height: 233cm
 * Weight: 168kg
 * Punching Power: 40t
 * Kicking Power: 80t
 * Maximum Jump Height: 100m
 * Maximum Running Speed: 100m/1s

The final form Hibiki was able to reach is known as Hibiki Soukou or Armed Hibiki. To reach this form, Hibiki must use the Armed Saber, the Armed Saber also serves as a weapon in this form. When initiating the call Hibiki automatically assumes Kurenai Form. Hibiki calls upon the power of the Disc Animals to fuse with him, each becoming armored for his form. Finally, his oni face is covered with a samurai like shield and his horns expand a bit. Though his transformation was unlocked through Tsukasa's K-Touch. Hibiki is able to destroy most lower level Makamou with little to no effort in this form.

Armed Hibiki is also able to execute a fiery Rider Punch; shown on Movie War 2010.

Final Form Ride
Decade's Final Form Ride allows Hibiki to change into Hibiki Akanetaka (ヒビキアカネタカ (茜鷹)), then when Decade activates the Hibiki Final Attack Ride Card, Hibiki Akanetaka transforms into the Hibiki Ongekiko (ヒビキオンゲキコ (音撃鼓)) to deliver the final blow.

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.