In the context of the game produced by shizuka, the process of people becoming demons is not explicitly detailed in the provided information. However, the game's premise involves a setting where "demons" are hidden within a closed women's dormitory, and the player's role is to uncover which of the two encountered girls is the "demon" through conversations and clues.

Given the nature of the game as a short adventure with horror elements, the transformation or identification of a person as a demon likely involves uncovering hidden aspects of the characters' identities or behaviors through the gameplay. The game's focus on dialogue and clues suggests that becoming a demon might be more about a revelation or a narrative twist rather than a literal transformation.

For a more detailed understanding, players would need to engage with the game directly, as the process of identifying or becoming a demon is part of the game's mystery and storyline.