Dennou Gakuen
Platform: PC98, X68000
Publisher: Gainax
Game: Adventure, Quiz
Difficulty: 3
Nudity: 4

In this series of games, you wander around a school talking to people and eventually running into girls who quiz you. If you pass their quiz with an average of 80% or more, they strip, and continue to do so with each round you pass. Their state of undress is also reflected in their picture as they quiz you. This first game pits you against three girls.

Screenshots from the PC98 version.