The Catholic high school for girls, St. Sophia, has a reputation of a very traditional establishment with strict rules. However, there are also rumors that after midnight, something mysterious happens to the school, and everything inside it changes... When the protagonist, a substitute teacher, arrives at St. Sophia for a three months teaching job, he quickly discovers that the behavior of the school inhabitants is anything but compatible with the Christian morals...

Tenshitachi no Gogo 4, like most other games in the series, is a fresh start story-wise; from gameplay point of view, it plays just like its predecessors: it is a traditional Japanese adventure, without puzzles and with menu-based interactions, with verb commands and sub-menus of objects. Usually the game allows the player to advance only upon depletion of all the possible commands. There are, however, right and wrong decisions, including story branches that will end in a Game Over.