Until I, a Supporting Character, Became the Heroine

Louis wakes up in a mysterious dungeon, where he meets Claude, who saves him from a monster, and realizes he's been transported to another world, the Tower of God, the setting of a popular otome game. The other transported person, Mayu, has a mark that proves she is the heroine. However, Louis has no mark and cannot use magic. In order to return to his original world, Louis accompanies Mayu as a burden mob character, despite being bullied by her. Meanwhile, as Louis connects with the capture targets, the mark of the heroine begins to appear on him──!? Will he take the place of the heroine in the labyrinth dungeon?! A great reversal love fantasy begins. (Source: Kadokawa, translated)