Sotsugyou Vacation (1997)

Sotsugyou Vacation is a love adventure game and part of the Graduation series. It is a sequel to Sotsugyō Crossworld, featuring the cast from that game plus three new characters. The player joins some of their classmates on an island summer vacation; the island turns out to be kind of boring, so after hearing a story about hidden treasure somewhere on the island, some of the girls decide to spend their time looking for that treasure.