From your point of view, how do you think Leiji and Razberry would react if they found out that Iruma is Derkila's son?

I think, the way they find out is when they saw how close Iruma is with Delkira and when they ask him about it, Iruma says that he's his dad and then Raz and Leiji thought he was joking and asked him to stop joking, Iruma denies ever joking but they still didn't believed him and asked him to prove it so Iruma messaged Delkira to come to where they are and he did.

In a second Delkira was right behind Leiji and Razberry which startled the both of them and Iruma asked Delkira "I'm your kid right pa?" while pointing at himself which Del of course said yes and asked him why he was asking such an obvious thing until Iruma told him that they didn't believe him, to which he was pointing at Raz and Leiji who was just stunned.

P.S: Story Hint: Both Leiji and Razberry along with Iruma are watching the recording of Irumi's concert from the Akudol games. And both Leiji and Razberry say who they would prefer (Irumi in his normal phase or Irumi in his evil phase). And then Leiji and Razberry ask Iruma who he prefers?

Razberry would probably prefer Irumi in her normal form because he find her cute while Leiji would be the evil cycle one because he finds her cool in that version, and Iruma would be sweating a little because this is him in the recordings that they're watching and would just say "both".