Seisai
English title: Perverse Investigations
Japanese title: 性裁
Alternative titles: Sex Judge
Type: OVA
Source: Visual novel
Episodes: 2
Status: Finished Airing
Aired: Jan 10, 2003 to Apr 11, 2003
Duration: 28 min per ep
Rating: Rx - Hentai
Studios: Y.O.U.C
Producers: Digital Works
Licensors: Critical Mass Video
Genres: Avant Garde, Fantasy, Horror, Hentai

A horrible murder has been committed on the grounds of Nankai Academy. Professor Yuko, one of the school's most popular teachers, died when she was pushed off of the roof of one of the school's buildings. Her death has left her students with feelings of confusion, pain, and above all else... anger. Four of her male students, Masayoshi, Daisuke, Mitsuru and Shinya, are determined to uncover the truth. They soon discover an important clue: Professor Yuko's planner had been marked on the very night she was killed... marked with the names of seven girls. 

With this evidence, the boys begin their investigations... and they'll use any method required in order to find the murderer. Through rape, manipulation and torture, they uncover important details, but piecing the puzzle together won't be easy. And the longer their search draws on, the more they feel themselves being overtaken by their own dark desires... Will they ever find out the truth behind Yuko's death?

(Source: ANN)