I've Been Killing Slimes for 300 Years and Maxed Out My Level

Aizawa Azusa accidentally works herself to death at 27 years old; she is reincarnated as an immortal witch and finds the experience of killing slimes for 300 years makes her the strongest adventurer in the world which results in daily challenges.

After dying of overwork in the real world, Azusa Aizawa is reincarnated as an immortal witch and spends 300 years enjoying a relaxing life and killing slimes. As soon as he reaches level 99, people rush in to challenge the world's strongest.

Leila is getting married; Azusa and her friends set off to visit Mount Rokko, the home of the Red Dragons.