RapeLay is played from the perspective of a chikan named Kimura Masaya, who stalks and subsequently rapes the Kiryuu family (a mother and her two daughters).
The player can choose from a variety of sexual positions, and controls the action by making movements with the mouse or by scrolling the mouse wheel. It features a realistic sexual simulator which allows the player to grope and undress the characters on a crowded train. Later, the player may have forced intercourse with all three women at his leisure. The player has a variety of sexual positions to choose from such as woman on top, forced fellatio and threesomes. RapeLay also has a "nakadashi" (internal ejaculation) counter, which carries a danger of pregnacy.