Cat Quest III

The Lovepurr dungeon can be found in the NE section of the map. To complete it, you first need to find three associated books, then return to the tower for a choose-your-own-adventure story and a few boss fights. I am not 100% sure if the order of the choices in the story matters as I never "failed" one, and I have no idea if I somehow magically chose all the correct answers, but the video below will lead you to the books and gives the answers that the creator used to complete them, so do that to be safe. Once you defeat the boss and speak to the NPC back in the lobby you'll complete the quest and unlock this achievement.