Oni (Hibiki)

Oni (鬼, lit. "Demon") is an incredible hero who has acquired great combat ability, through intensive training and the use of advanced equipment, created by TAKESHI's organization. Their weapons are designed with a musical instrument called as Ongeki Weapon, which producing the 'pure sound' to purge the evil spirits of the Makamou.

In the TV series, there are a total of 113 active Oni in Japan, a total of 12 active Oni are seen in the show (as seen in the opening, although Shuki does not appear in the opening), but only 8 have shown up in the series (the only 4 who did not show up were Gouki, Shouki, Banki, and Toki). There were also other Oni who did not make appearances and were just mentioned. 5 more Oni are introduced in The Seven Fighting Demons, the movie spin-off of the TV series.

Name
However, they are all generally referred to as Sound Attack Warrior (音撃戦士 Ongeki Senshi), but they are called Oni most of the time. The title of every Oni bears the -ki suffix (鬼), which is semantically identical to "Oni" in Japanese. It also has some resemblance with the real name of the Oni.

Story
Oni are mostly unknown outside their organization in the present day, but were oftentimes feared in the past for their power and shunned for "sacrificing of their humanity" by becoming Oni. Oni follow a one-master-one-apprentice tradition. Upon the retirement of their master, an apprentice will inherit the responsibilities as well as all equipment from his or her predecessor. He or she will often inherit the master's title too, but there are exceptions. When a person transforms into an Oni, the persons' clothes are often burnt up or sliced to pieces in the process, though there are ways to learn how to prevent this from happening. If an Oni fights relying on his or her anger, the forehead emblem will grow over the face. When an Oni becomes evil, the headquarters decide if they should be eliminated. If they decide to eliminate the Oni, they send someone from the head family to carry out the task.

Sound Attack Warrior
A warrior who has trained the mind and body by training and has acquired the ability to transform into a battle form called "Oni". It is divided into several groups depending on the system of their Ongeki Weapon used (in the TV series, there are 3 systems: Drum Demon (鼓の鬼 Tsudzumi no Oni), Tube Demon (管の鬼 Kan no Oni), and String Demon (弦の鬼 Gen no Oni)), and the pros and cons of the tactics are different.

They have an unusually shaped body that emits a gloss as a feature of appearance, the decoration depending on what kind of Ongeki Weapon were used (on chest, wrist, and ankle). There is no eye nose on the face, and things like eyebrows are bordered. The horns grow on the top of the head, and on the forehead, the same Oni's face emblem appears on the forehead as on the transformation devices called Demon Face (鬼面 Kimen).

Unlike other riders, they did not wear a mask or any kind of suit, but its their true form.

Transformation
An Oni makes a demon face appear on the forehead by bathing a special sound wave emitted from the transformation tool, and transforms into an "Oni" who controls the power of the attribute. At that time, the clothes worn were burned and torn and lost, and after transformation they would be naked if they were not trained enough. In addition, because transformation consumes a great deal of mental power and energy, it can not transform unless trained to a level that can withstand it. The transformation tools identified in the TV series, they are 3 types: Onsa, Onibue, and Kigen.

Means of Combat
After being Oni, a person's physical capabilities are upgraded. Called as Kitōjutsu (鬼闘術, lit. "Demon Battle Technique") and Genjutsu (鬼幻術, lit. "Demon Phantasm Technique"), Oni uses a special power, enough to deal with Makamou:
 * Extraordinary Strength: Oni has twice the strength compared to ordinary humans.
 * While Hibiki defended himself from the Yamabiko attack, also during a fight with Ooari. These two Makamou weighs over 5 tons.
 * While Todoroki was gripped by Bakegani's slab, broke it and stripped himself, as well as pulled Amikiri (Makamou weighing more than 6 tons) who trying to escape.
 * Extraordinary Speed: Oni is able to moving fast and nimble.
 * High Jump: Oni is able to jump at high altitude.
 * Hibiki jumps and kicks towards Nurikabe (8 meters high).
 * Eiki jumped about 8 meters to save Todoroki from the mouth of Tsuchigumo.
 * High Resistance: Oni has a higher endurance than normal human beings.
 * As opposed to Kappa, Hibiki's hands were hardened with the Makamou's saliva, then attacked him in the nearby river. However, Hibiki can still move and be able to fight well.
 * While Ibuki was against Oonamazu in the water, he was still able to launch his Ongeki Finisher attack.
 * Healing Ability (治癒能力 Chiyu nōryoku): The ability to recover physical injury is faster than normal.