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

After becoming the strongest in the world before she even knew it, Azusa entered into a new lifestyle with her first pupil, Laika the dragon, and discovered fun and enjoyment in it that she hadn't known before. But then, one day, a young girl calling Azusa her "mama" shows up and proclaims that her younger sister wants to kill Azusa. But Azusa has no memory of giving birth to these two girls, or of becoming a mother at all...

Halkara has built a new Nutri-Spirit factory in a nearby town and is now regularly going there from the cottage in the highlands, but she comes home exhausted every evening. It seems rumors have spread saying there's a ghost showing up at the factory, so she's had to do all the work alone since all the locals are scared to go there. Azusa doesn't deal well with ghosts at all, but she can't bear to let Halkara work herself to exhaustion, so she summons Beelzebub to help and heads to the factory late at night.

Azusa receives an invitation from Beelzebub to attend a ceremony in the land of the demons. It seems she earned a favorable reputation with the demons after stopping the conflict between the two Dragon clans in Laika's homeland. Azusa invites the whole family along for this high honor, but there's one problem: Rosalie, the ghost, can't wear a dress. But Rosalie is part of the family, and Azusa wants to help her dress up like the rest of them, so she uses the power of her maxed level to create a magic spell...