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

TMDB score: 7.8/10

After dying of overwork in the real world, I’m reincarnated as an immortal witch, and I spend 300 years enjoying a relaxing life. At some point, though, I end up at level 99! All those years spent killing slimes to make the money to pay the bills gave me a ton of experience points. Rumors of the level 99 witch spread, and soon I’m up to my ears in curious adventurers, duelist dragons, and even a monster girl calling me her mom! I’ve never been on an adventure, but I’m the strongest in the world… What’s going to happen to my relaxing life?!

Selected season 1, episode 1.