So I'm a Spider, So What? Ruler of the Labyrinth is collaborating with That Time I Got Reincarnated as a Slime. In this collaboration, over 10 characters from "That Time I Got Reincarnated as a Slime", including Rimuru, Milim, and Diablo, will appear in "So I'm a Spider, So What? Ruler of the Labyrinth." Players will be able to explore the labyrinth alongside collaboration characters, and equip the protagonist with items inspired by the world of That Time I Got Reincarnated as a Slime. Various in-game events are planned as part of the collaboration.