One of the better eroge adventure games for the PC-98… if you can make it through the backstory. Seriously, this game feels like they were going for some kind of award for longest time to get to the title screen and actual gameplay. Basically, you and your friends end up lured to an abandoned school, where you try to escape and the titular Isaku attempts to kidnap and rape your companions.

The adventure parts involve you interacting with characters via a contextualized mouse pointer when you hover over the object. There's also kind of a pseudo-3D dungeon crawl around the school, which takes you to the various rooms where the adventure interface takes over once more. There are puzzles to solve to escape, and you need to find your kidnapped companions before Isaku rapes them, if you are going for the best ending.