This is just my opinion, but the fact that Youko and the king of En wind up joining the armies of rebellions full of people that explicitly consider them enemies. It was hilarious when Youko did it. It was hilarious when En did it. It was more hilarious when he was meeting and chatting with The Dragon who had no idea who he was rebelling against.
Shoukei casually tells Rakushun her initial plan to get close to Youko and usurp the throne from her (by this point she's given up on it after some Character Development). The sudden dramatic music and his Oh Crap! face afterwards while choking on his food is what really sells it.