Denji is robbed of a normal teenage life, left with nothing but his deadbeat father's overwhelming debt. His only companion is his pet, the chainsaw devil Pochita, with whom he slays devils for money that inevitably ends up in the yakuza's pockets. All Denji can do is dream of a good, simple life: one with delicious food and a beautiful girlfriend by his side. But an act of greedy betrayal by the yakuza leads to Denji's brutal, untimely death, crushing all hope of him ever achieving happiness. Remarkably, an old contract allows Pochita to merge with the deceased Denji and bestow devil powers on him, changing him into a hybrid able to transform his body parts into chainsaws. Because Denji's new abilities pose a significant risk to society, the Public Safety Bureau's elite devil hunter Makima takes him in, letting him live as long as he obeys her command. Guided by the promise of a content life alongside an attractive woman, Denji devotes everything and fights with all his might to make his naive dreams a reality.

Unaired ep.13 included on BD/DVD.

Nuclear testing has resulted in the abrupt evolution of the Fumoon, a tiny but highly intelligent humanoid race on a small island, who are detected by Dr. Yamadano. Except for a few witnesses including the detective Shinsaku Ban, and the young men Rock and Kenichi and Kenichi’s sister Pichi (Pinoko), no one believes him. The Fumoon are kidnapping animals from around the world to bring with them as they use their space ships to evacuate the earth, because they know Earth is shortly to be destroyed by an enveloping cloud of black gas created by a stellar explosion. The Fumoon intend to abandon mankind, but one Fumoon, Rokoko, who becomes good friends with Kenichi, tries to help Dr. Yamadano and the others to develop a space ship to allow a few humans to escape, with the help of Dr. Ochanomizu and Dr. Frankenstein.

A compilation movie of the TV series containing a newly added footage.