Immoral Study is a rather straightforward tale of seduction. Do everything right, and you get your way with the lovely student. Commit one fatal mistake (this can only happen at one point in the game) and you land in jail.
There have been two sequels (or should I say additional episodes), the original game has been re-released in 2000, but seems to be sold out meanwhile.
What's amazing about this game is that there is animation involved, especially when you start having your student's clothes removed and when you actually begin to fondle her private parts. Of course, this animation is ever present when you do get past her defenses and go for it like a wild rabbit gone lose. Another thing I liked about this game is that the Professor's face (quite a handsome one at that) can actually be seen, when most bishoujo games hide the main character's face from view.
Immoral Study also brings the innovation of video to the Hentai genre. Although EVE Burst Error also had animated segments, EVE was also not truly Hentai, and thus didn't make use of it's innovation for intimate scenes. (Come to think of it, neither did Desire...) Immoral Study does, and it works well. The animation is clean and effective, though a bit pixelated at times.
To say the game is simply short would be an understatement. I completed the game in ten minutes. This is no exaggeration. Okay, I'm a quick reader and I wasn't staring for hours at every picture of naked Reiko. But even if you try hard, there is no way you could extend the life of this game for more than one average gaming session. It is so short that you feel you were simply cheated after completing the game.