Season 1 of Urotsukidōji: Legend of the Overfiend premiered on January 21, 1987.

Planet Earth is not all it seems. It is revealed that humans are not alone and that there are unseen realms running parallel to our own: the realms of the Demons (Makai) and the Man-Beasts (Jyujinkai). To further that, there is a 3000-year-old legend that foretells the coming of the Overfiend (Chōjin)—a being of unimaginable power that will unite all three realms into a land of eternity.

The story follows the exploits of the protagonists—man-beast Jyaku Amano, his nymphomaniac sister Megumi and their companion Kuroko—as their 300-year search for the Overfiend takes them to a high school in Osaka, Japan. Their discoveries led them to two students: shy, lecherous Tatsuo Nagumo and school idol Akemi Ito. But as the film plunges deeper into the dark and gruesome, Jyaku discovers that the Legend of the Overfiend is not what it seems and that the future of the three realms may be strikingly different from what he is led to believe.

Season 2 of Urotsukidōji: Legend of the Overfiend premiered on December 1, 1990.

Unbeknownst to Jyaku and Megumi, in 1944, the Nazis attempted to summon the Overfiend's nemesis: the Lord of Chaos (Kyō-Ō). Top scientist Dr. Münchhausen and his son invented a perverse death-rape machine to summon the Lord of Chaos—but the machine overloaded; and helped to destroy half of Berlin—leaving Münchhausen II alive, but psychologically scarred.

During his adolescence, Münchhausen II discovers his father's journal and tries to uncover the secrets of the Jyujinkai and the Makai. He finally succeeds and reawakens Kohoki—a demon banished to hell for eternity—into the human realm and the two form an infamous partnership.

Cut to the present day and Münchhausen II is trying to fulfill his father's work—to summon the Lord of Chaos—but to make sure it will work this time, he needs a human sacrifice. And it just so happens Tatsuo's cousin Takeaki Kiryu is on the next plane to Osaka...

Season 3 of Urotsukidōji: Legend of the Overfiend premiered on October 1, 1992.

Twenty years have passed and the Chojin has been prematurely born. He summons Jyaku Amano to protect him and to help to discover what has happened, sending Jyaku forth to search for the evil born in the east. Unfortunately a new race called the Makemono (Demon-Beasts) have arisen following the apocalypse, ruled over by the fanatical cyborg Caesar and his mysterious comrade "Faust". It is apparent they are the cause behind these events and intend to resurrect the Kyō-Ō.

Jyaku, along with the Makemono Buju and Caesar's traitorous daughter Alector, need to stop the two dictators from ruling the land of eternity. The question is, who will succeed?

Season 4 of Urotsukidōji: Legend of the Overfiend premiered on December 21, 1993.

Continuing straight after the climax of Return of the Overfiend, Jyaku and the survivors head for Osaka to help the Overfiend after his climatic battle. On the way they find a kingdom where children rule over adults (OVAs 1 and 2). Jyaku's problems are furthered when an old nemesis shows up at the wrong time (OVA 3).

Season 5 of Urotsukidōji: Legend of the Overfiend premiered on December 28, 1996.

After giving birth to the Chōjin, Akemi reawakens in a hospital, along with Jyaku, who had barely survived a recent confrontation with the Chōjin (whose form constantly mutates between male and female). Destroyer God Tatsuo also reappears (after supposedly being killed by Kyō-Ō in Urotsukidoji: Return of the Overfiend) and continues his ravaging of Earth. Still in love with Tatsuo, Akemi runs out to find him.

Meanwhile, Jyaku is confronted by some of the Chōjin's new 'children', and engages them in battle. However, his efforts prove almost futile, as they are constantly regenerated by the Chojin. Akemi eventually finds Tatsuo, still in his God form, and pleads with him. He clutches her in his hand (similarly to the end of the first episode) and prepares to kill her. However, she is rescued at the last minute by Jyaku, although she condemns him for doing so.