"I understand you, I understand. Well, don't mind me if I ask, but can I see the official document signed by the Patriarch himself?" Oumu asked Rouge.
What he asked was something that could be considered to be crossing the line and excessively rude and it could be misunderstood as Oumu not believing Rouge even after saying those words earlier.
After all, asking to see the official document signed by the Patriarch himself...is just impossible.
The official document signed by the Patriarch is what put Rouge in the position of the Temporary Patriarch of the Warmester Denoble House.
If Rouge gives that to Oumu and then Oumu destroys it or anything of the sort, then one could say that Rouge no longer has the right to become the Temporary Patriarch of the Warmester Denoble House.