From the introduction:
Welcome to XII: Inner Demons, a roleplaying game of trauma, turmoil, and diabolic danger. Set in a world much like our own, this game will follow the path of a human whose own internal strife and traumas have drawn the attention of a monstrous Archdemon, a creature far removed from reality who seeks to devour them and their delectable suffering. Suddenly thrust into the supernatural world and with a twelve day timer before the Archdemon arrives, they have to team up with other humans and lesser demons to either break the anchors allowing the monstrosity to manifest, or to solve their own traumas before they can be used to welcome the Archdemon into their world. You will face danger and terror, be it from demonic servants to possessed mortals to simply the frailties of being a human stealing precious time. Whether you can pull through the twelve days and survive against your greatest fears and darkest secrets, that’s up to you.