The Kubera audio drama CD was released in April 2016. It contains three side stories found only within the CD. It can be purchased from Naver here.
The side story descriptions from the audio drama are as follows:
Supplemental story 1: The Goalkeeper is a God
After Agni's shocking revelation in Season 2 Episode 3...
What is the truth behind the rumors that are quickly spreading among the citizens of Atera?
This is the delightful story of the priestess, the God and
the Dragonny, and the house masters of Atera.
Supplemental story 2: Teo's Cooking Lessons
After watching Gandharva demonstrate how to peel apples,
Teo is distressed and decides to learn how to cook.
But why are there sounds of explosions coming from the kitchen?
Is that really the right way to cook?
Supplemental story 3: The Strongest Half
Leez wants to go to the Martial Arts Academy once more,
but since Ran has half-blood phobia,
this time she goes with Yuta...
Who do they encounter there?