The provided text appears to be a description of a game rather than an answer to the question "How do people become demons?" To address the question directly while maintaining the context of the game, here is a response that incorporates elements of the game's narrative:

In the game produced by shizuka, "How do people become demons?" is a central mystery that unfolds within a closed women's dormitory. The story follows the protection bureau staff tasked with safeguarding a "demon" and their interactions with two girls who appear to be dormitory students. Through a series of conversations and clues, players delve into the enigma of demonic transformation.

While the game does not explicitly detail the mechanics of becoming a demon, it suggests that such a transformation might be linked to the hidden secrets and supernatural elements within the dormitory. The narrative implies that understanding the true nature of the "demon" involves unraveling the backstory and motives of the characters encountered.

To explore this further, players must engage with the game's short adventure, which lasts approximately 20 to 30 minutes. The game, created using RPG Maker MV and featuring various plugins for enhanced gameplay, offers a unique experience that blends horror elements without overt threats, focusing instead on the mystery of demonic identity.

This response keeps the focus on the game's narrative and the question about demonic transformation, maintaining the SEO-friendly structure and avoiding any extraneous content.