Magical Explorer, Vol. 9 (light novel): Reborn as a Side Character in a Fantasy Dating — Sim Iris

With his game knowledge and trusty stole, Takioto attempts to clear the 60th floor of Tsukuyomi Academy Dungeon in record time. Meanwhile, he can't help but worry about Katorina, who seems to be changing for the worse in pursuit of power. When a demon reveals the secret story of her birth, the line between humans and demons grows shaky, and Katorina falls to the dark side. Can Takioto bring her back to her senses?