i have a stupid cuestion. when did diablo start serving rimuru? maybe is because i watch all seasons in a week but i don't recall it happen.
great episode btw, rimuru is not a demon slime, is a omnipotent slime XD
Diablo technically starts serving him in the next episode I believe, but he has been trying to get summoned by Rimuru before which is when Rimuru summoned the demon for Ramiris in S1.
I hope this explanation helps