I've Been Killing Slimes for 300 Years and Maxed Out My Level Novel Volume 5 is written by Kisetsu Morita with illustrations by Benio.

I'd been killing slimes for 300 years-and then I had to go into a huge dungeon! I didn't really want to go at first, but after exploring it, I finally discovered that the exciting life of an adventurer...is probably still not for me. (Maybe a little?) Then there was that visit to Beelzebub's house and sending my daughters to school-things have gotten so busy I've almost forgotten how to take it slow!