Aizawa Azusa, a corporate drone who died of exhaustion from overwork in her previous life, is reincarnated in another world, where she decides to live out a slow and uneventful life forever. But then, 300 years later, she discovers that the experience she earned by defeating slimes every day just to keep up her easy lifestyle has brought her to level 99 and made her the strongest in the world. The rumors begin to spread, and soon trouble comes knocking...

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...

Halkara throws a mushroom-grilling party, or "shroompa" for short, and accidently includes some poisonous mushrooms that cause anyone who eats them to shrink... and Azusa eats one. This leads to everyone ridiculing her—or rather, fawning over how cute she looks. Even her daughters are in on it! Azusa is determined to change back to normal, so after a tip from Pecora, she heads to the World Tree along with Fatla and Vania to find a pharmacist who deals in every kind of medicine. She expects a dungeon with 108 floors to fight through, but...

Festival season has come to the village of Flatta. The festival has been held there for the past 250 years, but as the only person who knows its entire history since it was started, Azusa has distanced herself from it to let the villagers keep their independence. But her family has shown interest in it and seems excited to see it, so she makes up her mind to change the way she interacts with the village tradition... and thus the one-day-only coffee shop, The Witch's House, was born. Will the villagers enjoy this little shop Azusa's family has created?