UndertaleFanfic, x Reader & AI Roleplay

Undertale is a role-playing video game in which the player controls a child who has fallen into the Underground, a vast region beneath the surface of the Earth that is sealed off from the outside world by a magical barrier. On the journey back to the surface, the player encounters various monsters, some of whom lead to combat. Battles involve dodging bullet-hell-style attacks, and rather than simply defeating enemies, the player can choose to appease them and spare their lives instead.

A defining feature of the game is that choices between fighting and sparing shape the dialogue, characters, and overall story, meaning the same encounter can unfold very differently depending on the player's approach. This branching structure encourages replay and reflection on each outcome. The game is noted for its distinctive combat system, music, memorable characters, and the emotional weight placed on player choice. These elements make the relationships between the protagonist and the monsters, as well as the game's differing endings, popular subjects for fan works.