The first night-Yuumi is raped by a sexual molester on her way to school. She cant cry out. He violently molests her over and over again. Somehow she escapes from him but ever since thin she feels as though someone is watching her all the time in the toilet, in the shower, wherever she is, someone's eyes follow her. 
The second night- The haughty woman fashion designer blames a subordinate who made a mistake. Soon she becomes imprisoned, totally nude, inside of the public telephone booth. But it was just the beginning of the revenge 
Third night (Inside of the water) Izumi Hinagawa is the star of the swimming club to who all the aspire. Aki Sakuragi was one of them. In the shower room, Izumi found a white panty inside a plastic bah that someone had forgotten. She confirms that it belongs to Aki. Ixumi slowly opens a panty and presses it to her nose. She said "Aki". The truth is Izumi is a lesbian and has feelings for Aki. Then, the next day, Izumi approaches Aki at poolside. From this moment, they are guided into the sexual world. Dear angels you shall experience the pleasure of paradise. 
Fourth night (The Box) when Aoi wakes up she is in the dark and there is a wall of concrete on all sides. There is only a bed frame, the light In the ceiling and the iron door. Aoi is startled when the door opens and then locked. Then, men rape Aoi by turns. She is humiliated and tries to remember, "How long have I been here?" The reality is that her state between the real and fantasy began when she opened the little box that she bought from the strange antique shop. 
(Source: AnimeOnDVD)

Inmu: Feast of Victims