Hitoshi Hidaka, known simply as Hibiki, is the main protagonist of his respective narrative, a seasoned warrior who has dedicated his life to protecting humanity from monstrous creatures known as Makamou. As an Oni, he is a being who transforms into a demon-like form to combat these threats, though his true nature is that of a calm and principled man. He was not born a demon; rather, he began his training at the age of sixteen, a decision that stemmed from a desire to protect his friends, much like the young people he would later mentor. At the age of thirty-one, he is one of the most experienced Oni in the Kanto region, known for having surpassed many of his predecessors by being the first to wield a powerful weapon called the Armed Saber.

Hibiki possesses a personality marked by a strong sense of ethics and a remarkably relaxed and nonchalant demeanor. He is an open and straightforward individual who can quickly befriend strangers. His defining characteristic is his unwavering dedication to constant training, which he pursues not out of anxiety, but from a firm belief that consistent self-improvement is the key to success. As a result of this philosophy, he is seldom seen worrying, trusting in his rigorous preparation to see him through any challenge. This attitude, combined with his wisdom and experience, causes other Oni and allies to naturally look up to him as a teacher, even though he humbly views himself as just another fighter in the endless war against the Makamou. One of his most recognizable quirks is his signature salute, which he often accompanies with a casual "Yo!" as a greeting or farewell.

Despite his prowess in battle, Hibiki is not without his limitations, particularly when it comes to modern technology. He has difficulty using computers, sending emails, and initially did not even own a cell phone, often relying on public telephones or the phones of his supporters to communicate. This contrast between his ancient, mystical way of life and the modern world further grounds his character.

His primary motivation is a simple but profound desire to save people and live his life to the fullest, a creed he repeats to himself and others. This philosophy is not just about defeating monsters but about embracing life itself. He shares a deep, long-standing friendship with Midori, a woman who designs weapons for their organization, having known her since they were children. His role in the story is significantly defined by his relationships with two young men, Asumu and later Kyosuke. He takes Asumu, a boy he saved from an attack, under his wing, offering guidance and advice as Asumu navigates his path to adulthood. Hibiki acts as a mentor, though he is hesitant about his own teaching abilities, partly due to a past loss of a student. He challenges Kyosuke's selfish reasons for wanting to become an Oni, emphasizing the importance of pure intent over personal glory. Through these relationships, Hibiki learns as much as he teaches, eventually realizing that Asumu's true path is not to become an Oni like him, but to find his own way, and he accepts this while promising to remain a mentor in life.

Throughout his journey, Hibiki undergoes significant development, particularly in his power and resolve. His training allows him to access two advanced forms. The first is Hibiki Kurenai, a powerful red form that nearly doubles his basic abilities, achieved through intense summer training. The second, and most powerful, is Armed Hibiki. To attain this form, he must master the dangerous Armed Saber, a forbidden device that caused him and another Oni to temporarily lose their ability to transform when they first tried to use it. Through grueling rehabilitation and training, Hibiki not only regains his powers but successfully masters the saber, allowing him to fuse with mechanical Disk Animals to create powerful armor and easily defeat formidable enemies.

As a fighter, Hibiki is a Taiko-type Fire Oni, whose abilities are intrinsically linked to sound and fire. He transforms by tapping his tuning fork, the Onkaku, against a solid surface, which engulfs him in a purple aura and reveals his demon form. Unlike many other heroes who wear suits, his Oni form is considered his true form, marked by a second demonic face on his forehead. In combat, his primary weapons are a pair of drumsticks called the Ongekibou Rekka, which he uses to strike a circular disk on his belt known as the Ongekikou Kaentsuzumi. By attaching this disk to a Makamou and striking it with his flaming drumsticks, he unleashes a powerful purification sound, known as an Ongekida, that destroys the monster. He also possesses retractable claws and a breath weapon, as well as superhuman strength, speed, and leaping ability. Later, his signature vehicle becomes the Gaika, a large and powerful motorcycle he learns to ride specifically for his duties. He also utilizes Disk Animals, small disc-shaped devices that transform into animal allies for reconnaissance and combat support, which are crucial for achieving his final Armed form.