I've Been Killing Slimes for 300 Years and Maxed Out My Level: Along Came a Leviathan

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...