In the context of the game "How do people become demons?" produced by shizuka, the transformation into a demon is a central theme and mystery explored within the narrative. The game unfolds in a closed women's dormitory rumored to harbor demons, and as a player, you encounter two girls who are potential candidates for being the demon. The storyline suggests that becoming a demon might be linked to the environment or events within the dormitory, but the exact method or reason behind this transformation is part of the mystery you need to unravel through conversations and clues.

The game does not explicitly detail the process of how someone becomes a demon, as this is left for the player to discover through the interactive elements of the short adventure. The narrative focuses on the protagonist's journey to identify the demon among the two girls, hinting at a deeper backstory or set of circumstances that lead to this transformation.

For a more detailed understanding, players are encouraged to engage with the game's dialogue and clues, which are designed to lead to the resolution of this central question.