I've Been Killing Slimes for 300 Years and Maxed Out My Level Novel Volume 17 is written by Kisetsu Morita with illustrations by Benio.

I've been killing slimes for 300 years, and now I'm a magical girl?! Natalie and I have been turned into strange, mascot-like creatures, and together we protect the peace of Flatta... Wait, what?! Oh well, I know this is the work of some god or other, so I'm sure we'll soon have it sorted. Then, I accompany Flatorte on her visit home (along with the whole family) and attend Pecora's idol workshop! Finally, Wynona shares an adventure of her own.