Innsmouth no Yakata

Innsmouth no Yakata is a first-person horror video game where players assume the role of a private detective in 1922 who must escape from a monster-infested mansion with an artifact called the Necronomicon. Each stage in the game consists of a floor within the mansion, and on each floor players must find a key and use it to open an exit door under a time limit, which varies between levels. It uses a twin-stick-style control scheme with two directional pads, one for movement and the other for the player-character's gun. Completing each stage will present players with a stage select screen, featuring branching level paths similar to the Darius series. The game automatically selects a floor based on how much time is left upon completion; finishing in under 30 seconds lets players move up a floor, while finishing in the last 30 seconds forces them to move down a floor. After completing one of the final floors, the player-character escapes and the game ends.

Throughout the game, players encounter fishlike monsters that attempt to kill the player-character. These creatures can either be overcome with bullets or by fleeing. Additional ammunition as well as health pickups are found scattered throughout the various floors. A map screen shows players' current location and the layout of the floor, which will begin to reveal itself as players progress. Two kinds of collectible orbs can be found randomly placed on each floor. The white orbs reveal the entirety of the map, while the black orbs show the locations of items on that specific floor. The game features 45 different floors, though only 13 floors can be visited in a session. It features four different endings, including a "joke" ending that sends the player back to the start of the game.