In what has to be one of the favorite recycled hentai plots of all time, you play a shy male biology teacher at an all girl's school. You're actually undercover, investigating the disappear of the former teacher, who was also an agent, thus borrowing from the 2nd favorite recycled hentai plot of all time. It's a pretty much entirely linear adventure game, and you're not missing a lot if you just go to the CG gallery, which is unlocked. However, it does hook correctly with AGTH, so it is possible the play this game semi-translated.