A livestream for the "GA FES 2019" event on Saturday announced that author Kisetsu Morita and illustrator Benio 's I've Been Killing Slimes for 300 Years and Maxed Out My Level ( Slime Taoshite 300-nen, Shiranai Uchi ni Level Max ni Nattemashita ) light novel series is getting a television anime adaptation.

The ongoing drama CD adaptation's cast members will reprise their roles for the anime:

(The last two cast members will debut in the next drama CD which will come with the 12th light novel volume on April 15, 2020.)

Yen Press is releasing the novel series in English, and it describes the first novel volume:

After living a painful life as an office worker, Azusa ended her short life by dying from overworking. So when she found herself reincarnated as an undying, unaging witch in a new world, she vows to spend her days stress free and as pleasantly as possible. She ekes out a living by hunting down the easiest targets - the slimes! But after centuries of doing this simple job, she's ended up with insane powers...how will she maintain her low key life now?!

Yen Press will release the sixth volume on December 10. The company is also releasing Yusuke Shiba 's manga adaptation in English, and will release the first volume on January 21.

The novel series ranked at #9 in the 2019 edition of the Kono Light Novel ga Sugoi! guidebook.

Morita launched the novel series on the Shōsetsuka ni Narō website in June 2016. SB Creative published the 10th novel volume in print on August 9. Shiba's manga adaptation debuted on Square Enix 's Gangan Online website in June 2017, and Square Enix published the fifth compiled volume on September 12.

Morita also wrote a spinoff novel titled Hira Yakunin Yatte 1500-nen, Maō no Chikara de Daijin ni Sarechaimashita . Square Enix published the novel on September 13. The novel also has a manga adaptation by Meishi Murakami. Square Enix published the first manga volume on September 12.

Sources: GA FES 2019 livestream, Comic Natalie