Wicked City is a series of novels written by Hideyuki Kikuchi which has also been adapted into film and animation.
The story follows two members of the Black Guard, a force that guards the human realm from demon realm invaders. These two members are Taki, a human who has a salaryman job as a cover, and Makie, a demon living in the human realm with a cover as a model. The two are assigned as partners to protect a dignitary, but in truth both were born as a result of experiments by both humans and demons to make interbreeding possible. As a result of their partnership they fall in love and conceive a child which would usher in a new era of peace between the realms.
Many demons from the demon realm object to any sort of peace between the realms, beliving that demons should rule over humans. One of them seduces Taki in order to determine if he really is capable of having sex with a demon. After proving he can she roughs him up a bit, but only makes an attempt on his life later. She fills a tunnel with her webs, immobilizing Taki, Makie, and their car. She is caught off guard by the dignitary, however, and killed by a psychic blast.
Another demon attempts to kill the dignitary. After disguising herself as a Soapland girl she services the old man. While having sex with him she begins to absorb him into her liquid body. Taki and Makie arrive in time to save him, and after pulling him free Makie cuts off the demon's head.
One last demon is present at Makie's rape. When Taki appears to rescue Makie the demon uses her seduction power to hypnotize him. She compels him to enter her torso-sized vaginal orifice, but Taki is able to overcome her control at the last moment and blows her away with his spiritual gun.
The movie opens with Taki being seduced by a prostitue calling herself Perrie. "Perrie" reveals herself to be a spider Reptoid who has replaced a human prostitute. She and Taki fight, and she nearly kills him before she is killed by the sudden introduction of Taki's half-Reptoid partner Ken. Afterwards the two are sent to Hong Kong to track down the source of a Reptoid drug called Happiness.
Their search in Hong Kong leads them to a Reptoid businessman by the name of Daishu. In fact the source of the drug is Daishu's son, Shudo, who hopes to usher in an era of Reptoid supremacy. Working for Shudo is a Reptiod named Shira, who can transform her body into any shape, such as water, a clock, or a pinball machine. She attempts to swallow Taki and Ken by transforming into an elevator, but Daishu rescues them and forcibly rebuilds Shira into a motorcycle. She is killed when Daishu flips her off a ramp on the top floor of the building and she explodes on the street below.