Because the voice was angry, Oumu didn't know what to do in this situation.
He also didn't know what to say. After all, if he carelessly said something, it might just end up resulting in the source of the voice getting angrier than now.
That was why Oumu was trying to think up a solution to his current situation even though...death was literally knocking on his door's life.
Oumu was sure that the demon incarnate would be able to kill him in just a single second, so his current situation is too dangerous for him.
No, too dangerous is an understatement as Oumu can be killed without him even noticing that his life is gone.
That was why it was amazing for Oumu to be able to try and think up a solution in his current situation.
What's more, the demon incarnate's huge presence and heavy pressure were no joke. This is enough to make any demon panic and lose their composure.