Ichiro is an elderly man an intro about his life.

A high school boy Hiro Shishigami also gets mechanical body as Inuyashiki. He doesn't value people except for his mother and his friend Ando, and he starts to commit murders using his new power.

Shishigami confesses to Ando that his secret and his crime, it's a terrible shock to Ando. Inuyashiki is reunited fatefully with Shishigami. Inuyashiki works hard to help people using his power from the day after that.

Inuyashiki tries to punish a cruel yakuza Samejima.

Ando is struggling with the fact that his friend Shishigami is responsible for the spree of home invasions. After reading that hospital patients were being cured, Ando theorizes that there is someone else out there with the same powers as Shishigami. Ando lures Inuyashiki by pretending to need help and asks him to stop Shishigami. Meanwhile, Shishigami learns his mother has terminal cancer.

Shishigami is wanted for serial killings, he secretly stays with his classmate Shion Watanabe for a while. During that time, people severely criticizes Shishigami on internet, and his mother is deluged by the press. Meanwhile, Inuyashiki achieves mastery of his abilities with the cooperation of Ando.

Shishigami confesses to Shion that his secret and his crimes. Despite that she sincerely loves him. And she calls on him to reflect on his crimes while she is weeping.

Shishigami leaves the life with Shion and her grandmother. Meanwhile, Inuyashiki's daughter Mari finds that Inuyashiki and Ando walk together.

As the news reports on Shishigami's attack on the police station, Shishigami hijacks a broadcast signal to publicly declare war on Japan, claiming he will kill 100 people immediately. Ando realizes Shishigami's plans and manages to thwart it with the help of Inuyashiki's power. Undeterred, Shishigami continues his killing, and announces he will kill 1000 tomorrow, devastating Inuyashiki.

Many airplanes crash into Tokyo by Shishigami. Inuyashiki goes to the rescue some airplanes that is still flying, and tries to save victims including Mari.

Finally Inuyashiki confesses his secret to his family, and gets a warm reception. Meanwhile, Shishigami visits Ando, but he leaves for anywhere because Ando condemns him as evil. A few days later, the Earth faces an unprecedented crisis.