Individuals with Momotarou and Oni blood coursing through their veins maintain a longstanding rivalry. The Oni are careless, rash, and disorderly, while the Momotarou protect the human world from the uncontrollable Oni. Shiki Ichinose is a reckless and irresponsible teenager, aware of his defiance and even proud of his expulsion from school. Despite Shiki's rebellious attitude, his foster father, Tsuyoshi, cares about him deeply. Tsuyoshi's selfless love is soon shown in an explosive incident when a Momotarou barges in looking for Shiki. As a Momotarou himself, Tsuyoshi has been hiding Shiki for years and keeping his Oni origins a secret even from him. As he gives up his life to save Shiki and confesses everything in his dying breath, Shiki's Oni blood awakens for the first time, transforming him into an unruly monster overflowing with rage and a thirst for revenge. Shiki's momentary outburst attracts the attention of Naito Mudano, an Oni teacher at the Rakshasa Academy—an institution for young Oni in need of understanding and perfecting their powers. Before Shiki can avenge his father, he must learn to control his headstrong and impulsive nature and, above all, fight against his own demonic blood.

It is the Edo period. Ichitarou, the young master of Nagasakiya, one of the largest stores in Nihonbashi, has been in poor health since birth and is unable to go out. However, Ichitarou is always protected by demons such as Shirasawa and Inugami, who serve him. One night, Ichitarou goes out secretly and witnesses a murder. From that day on, bizarre murders begin to occur one after another in Edo... With the help of the demons, Ichitarou's search for the culprit begins!

Masahiro is the grandson of the great onmyouji, Abe no Seimei. However, he lost his sixth sense that enables him to see supernatural beings, which is very important for an onmyouji. Thus, he is left with no choice but to try and pick a different career. But one day, a strange mononoke appears, which he names Mokkun, who shows him his true potential powers after fighting a demon. With the assistance of Mokkun, his quest to become the greatest onmyouji begins.

Follow Liko and Roy as they unravel the mysteries that surround them and encounter Friede, Captain Pikachu, Amethio, and others during their exciting adventures!