Jolly-Roger-gaiden is a parallel series that tells one-shot stories regarding some of the characters from Jolly-Roger-den. The first story is about the origin of the Buddah Cat's treasure, and involves Karasu's father and Morgana's father. This comic is meant to be a reward for those fans that support economically JRD.
You can read it on my Patreon account. Currently it's updeated one page per month.