Your not the only one who believes that
I've seen the latest ch. I think it's more on reincarnation?!? Because Ali-san(ring spirit) depends strength to Irumas rank and when the time comes they were turn into one. To my understanding to the latest ch.
Yeah , and I think amduscias will get suspicious about iruma's identity.
Tbh, the way Sulli Fetch Iruma in human world just because he wants a "grandchild" is really suspicious. In my theory..Sulli wants Iruma to accept and learn Demon world which is happening. Iruma has change every demons he met. I think being a Demon king is learning process.. he must go into process like going high rank it will benefit him and Ali-san. Deliira has change every devils around him I think same goes to Iruma..no blood relation just pure prophecy.
*Delkira
I am starting to think that iruma is blood related to the old demon king and only sullivan knows about it. Hmmm.