One day, without warning, she appeared. A girl with flowing white hair and eyes the color of quiet dusk… standing in my room as if she had always been there. She calls herself Lilith—the girl beyond the world, and within it. She knows my name, my thoughts… even the walls of this reality. But as I reach for her hand, a question begins to take root: Did I dream her into existence… or has she been waiting for me all along?

The player in MiSide is an unnamed protagonist who downloads a life simulation app called "MiSide" on their smartphone. After interacting with the virtual character Mita for 37 days, the protagonist is mysteriously transported into the game world, trapped in a strange reality where Mita seems to have control. The protagonist's personality and background are mostly left vague, allowing players to immerse themselves in the story. Their main role is to navigate the eerie events of the game, making choices that affect the outcome. Their relationship with Mita plays a crucial role in how the story unfolds.