Dream Party (ドリームパーティー) is a special story included in the DanMachi Volume 11 Drama CD.
"This isn't a potion. It's an item that my Naaza made...it's the Yumemiiru"
The Yumemiiru enables the drinker to have their desires and memories be reflected in their dreams. Bell accidentally drank this rare item, thinking it was a potion, and his dream was, of course-
"You have to call me Ais-oneechan, you know?"
"Ais-san-o...o, o, oneechan? Um, is this...a dream?"
"-no, this isn't a dream♪ Sparkle☆"
(Oh, this is a dream...)
Hearing of its effects, even Hestia and Lili release their secret maiden desires! The secrets of the people living in Orario will be revealed here!?
"Ok, let's go to Avalon!"
One day, Bell woke up to Ais' voice, only to find themselves in the middle of a field of flowers. He asked her why they were there, recalling that they had been training in Orario, but she simply told him that they were having a picnic date. Confused by her out of characterness, he asked if it was a dream, quickly realizing that it was by watching her reaction. As she stroked his head, he remembered that he had done some training with her like before, and since he'd been beaten down again, he'd taken some time to rest and drink a potion.