I've Been Killing Slimes for 300 Years and Maxed Out My Level is a light novel series written by Kisetsu Morita. It follows the story of Azusa Aizawa, an ordinary office worker who dies in an accident and is reincarnated as an immortal witch in another world. She decides to spend her days leisurely killing slimes and maximizing her level. Along the way, she meets other adventurers, makes friends with them, and discovers secrets about herself and the world she lives in.