Girl Island is a game in which the player will immerse themselves in an atmosphere of lustful pleasures and erotic adventures in a bizarre, debauched land with elements of a fantasy setting. The protagonist unexpectedly finds himself on a mysterious island, with no memory of how he got there. The entire area is a mystery to him, and he knows nothing of his surroundings. Exploring the newfound space, the protagonist realizes he is not alone and that this land is inhabited by intelligent beings, but they are not human. The inhabitants he encounters turn out to be girls, anthropomorphic monsters from various mythologies elves, centaurs, mermaids, and fantastical androids.