Two years ago, the death of Naoto Watari's parents left him as the sole caretaker for his younger sister Suzushiro "Suzu" Watari and forced him to move in with their aunt. So devoted is he to Suzu that he refuses to join clubs or even hang out with anyone, earning him snide comments and the title of "siscon" at his new school. But as long as Suzu is safe and happy, Naoto doesn't care what everyone else says. However, his sneering classmates may turn out to be the least of his worries. The sudden transfer of a girl named Satsuki Tachibana brings back traumatic memories from his past—a past she had a hand in making so unpleasant. Nasty secrets, unknown to Naoto, begin to surface with her arrival, threatening his new life.

Early 2000s Tokyo. Isobe, a combatant for the evil corporation Ganglion, spends his days on the battlefield. Whether it's the "Tokyo Cedar Pollen Operation" or the "Mount Fuji Demolition Plan," he faces off in nothing but a bodysuit, only to be crushed by the hero Hopeman time and again. As he struggles under unreasonable bosses during the dawn of compliance, his story unfolds—a workplace drama dedicated to all who work, following the bittersweet life of a salaryman soldier.

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!

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.