1st Volume: Marina and Airi's mother divorced few years ago and got remarried recently to a young man. While Marina accepts her new stepfather, Airi detests him. Little do they know that really he's a pervert that sniffs their underwear and wants to make them his own by making a love drug that will turn Marina and Airi into a sex-hungry sluts. When Airi comes home and notices her schoolmate Sana giving him a blowjob, he sprays the drug on her. Now he will do with them whatever he pleases.

2nd Volume: One week after losing his wife in an accident, the father of the Makino family finds himself thinking the wrong thing about his four lovely daughters. When the rebellious Natsume gets into trouble at school, it's time for daddy dearest to administer some discipline of the sexual variety. Soon, he's giving the same treatment to motherlike Akira, over-achieving Haruka, and sickly Fuyu. Whether they want it or not.

(Source: AniDB)