The discovery

When Zenitzu came back to the dojo after a shopping trip to the village he heard the sound of a demon... and not just any demon. and uppermoon. Escaping from Uppermoon 1 frantically, Zenitzu realizes his adopted brother was now a demon. The very thing both of them had trained all their lives to kill. How was this going to work out? especially since they don't get along very well....