SOO IM THINKING. Alikred spelt backwards is Derkila. The missing demon king, did he get trapped inside the ring somehow? He said that neither of them can live in the demon world without each other. Derkila because there's no where else for him to go other than the ring, he might be trapped in it.
Iruma maybe because if he didn't have the ring he wouldn't be able to use magic/mana and wouldn't be able to survive in the demon world because he would've either died or been found out as human.
The way that Ali-san was woken up by a loud sound by Poro-chan, he was his friend? Musician? So maybe he can only be awoken by him and (maybe) get his form back if it gets played alot.
I'm just saying