Rui wakes up in a mysterious dungeon. She meets Claude, who rescues her from demons, she realizes that he has been transported to another world, the "Tower of God," the setting of a popular otome game. The other transfer, Mayu, has an imprint that proves she is a heroine. Rui, however, has no mark and cannot use magic. In order to return to her original world, Rui accompanies Mayu as a burden mob while being abused by Mayu. As Rui begins to connect with the object of her attack, the mark of the heroine begins to appear on her as well...! In a labyrinthine dungeon, she turns into a heroine! A love fantasy with a great reversal of fortune begins.