"Siren" is divided into stages, each taking place in one of ten areas in the village of Hanuda, and organized chronologically in a table called the "Link Navigator". In order to complete a stage, the player must accomplish a primary objective that usually involves reaching an exit point, subduing undead enemies called "shibito", or finding an item. Objectives in different stages are interconnected via a butterfly effect, and a character's actions in one stage can trigger a secondary objective in another stage.