Loud Kou yells a lot. He is fairly deaf and has no patience for anyone who fails to speak with enough volume. In any case though, you need his help in granting you access to Nahpui Quarter, so you can continue on your quest to become Weh no Su.
"I am sorry. If you want something you are going to SPEAK UP. I cannot make out ONE BIT of your MUMBLING!"
"If that is the LOUDEST you can talk, maybe you ought to try hand gestures instead. If you CANNOT manage with hand gestures, maybe you had best RUN ALONG."
To a character that already has access to Nahpui Quarter:
"You look familiar to me. You are that MUMBLER, are you not? Well, just let me know if you want to go INSIDE."
To a Factions character that has not done the Vizunah Square mission:
"I am sorry. If you want something you are going to SPEAK UP. What's that? No, this is not the way to Vizunah Square if that is what you are asking. To be honest, I cannot make heads or tails of your MUMBLING!"
Loud Kou may have been inspired by Officer Barbrady of South Park and / or Loud Howard of Dilbert. In addition, Kou in Mandarin Chinese is mouth, which would literally make this character a Loud Mouth.
Having the quest Finding The Oracle, he will say he knows Nika and knows where she is.