Sound of Drop - fall into poison is an adventure game developed by aiueoKompany. This game takes place in Manten Aquarium, located in the heart of Tokyo, where Mayu and Himeno, two junior high school students, investigate urban legends. As they delve deeper into the mystery, they catch a glimpse of Mayu's missing younger sister, Mari. The story revolves around Mayu's pursuit of her sister's shadow while navigating through a crimson aquarium. The game has three main story routes and over 30 endings, most of which are bad. The game's narrative is from Mayu's point of view, and the player can make choices that affect the game's outcome.