Stepmother's Sin

The story starts off with Yusuke watching another man have sex with his mother. Much to his dismay, his mother is thoroughly enjoying it and appears to have no remorse about cheating on her husband. We flash forward to the present day, and Yusuke’s father has been transferred to a distant office. Before he left, he married a new wife on paper but not in ceremony; Yusuke now lives only with his stepmother Misako and her daughter Shiina from a previous marriage.

After a brief toy and oral tryst with his cousin Mio, he contemplates his feelings for his new stepmother and women in general. In his mind, they are all filthy nymphomaniacs; they may act innocent, but they will act like sluts if given the chance. This thought and hatred for his mother consumes him and drives him to exact revenge on womankind through his stepmother.

Unfortunately, Misako does little to prove Yusuke’s theory wrong as she quickly gives in to Yusuke’s devious seductions. The first episode ends as Yusuke begins to show his cruelty in their lovemaking. The second episode picks the action right back up with Yusuke coming up with more ways to humiliate his stepmother while gratifying his sexual urges.

Meanwhile, Shiina dreams of making love to her half-brother. Unfortunately, her dream comes partially true as Yusuke forcibly takes her in front of Misako, humiliating them both. To make matters worse for Shiina is the fact that her mother ends up very aroused and begs Yusuke to take her. Shiina leaves for her grandfather’s place but ends up going willingly with three street punks; she lies back as they decide who gets her first thinking only of her mother’s actions.

One last tryst with his cousin Mio ends with Mio making Yusuke think about his actions. As he couples later with Misako, he realizes that he still hates his biological mother but has come to love Misako. He begs her forgiveness for his actions but receives a shock. She angrily rebuffs him and says that she does not care about his apology; she has grown to crave the rough sex he provides to the point where she cannot live without it.

Driven to a nervous breakdown, Yusuke runs off realizing that the true monster is not the woman Misako has turned into or women in general; instead, the true monster is himself, the creator of the beast Misako has become. These thoughts haunt him as he runs through a park eventually stumbling upon a couple making out. He assaults both of them and ends up crying on a park bench in despair and self-loathing until the police arrest him.

When the police bring him home, they find Misako engaged in an orgy; she sees Yusuke and begs him to come satisfy her needs. The scene shifts to the outside of the home as a struggle is heard. The last words we hear are "Stop, he's got a gun!" and then a single shot. It is left up to the viewer to decide which monster Yusuke has shot.

A Hentai OVA adaptation was produced by Digital Works and released by JVD months after the game was released. The same plot and characters were used. The OVA also expanded to show and extended the scene of Yusuke's Mother committing her first adultery and explained her reasons for doing so as well as how Yusuke discovered his mother's adultery. The OVA also featured an original ending.

• Dong, Bamboo (9 March 2003). "Shelf Life: Bananas and Computers". Anime News Network.
• Cruz, Luis (19 July 2003). "Stepmother's Sin". Mania. Archived from the original on 3 March 2015.
• Beveridge, Chris (1 October 2010). "Stepmother's Sin". Mania. Archived from the original on 26 August 2014.

• Stepmother's Sin (anime) at Anime News Network's encyclopedia
• Gibo at The Visual Novel Database