The player controls a child who has fallen into the Underground: a large, secluded region under the surface of the Earth, separated by a magic barrier. The player meets various monsters during the journey back to the surface. Some monsters might engage the player in a fight. The combat system involves the player navigating through mini-bullet hell attacks by the opponent. They can opt to pacify or subdue monsters in order to spare them instead of killing them. These choices affect the game, with the dialogue, characters, and story changing based on outcomes.

There are 3 main endings: Neutral, True Pacifist, and Genocide. This TAS achieves the Genocide ending, which is known for being the most RNG-intensive category in the game due to the heavy emphasis on combat; the player must kill a specific amount of enemies in each area in order to not lock themselves out of this ending.