If you're like me and can't seem to find the Otomo Couriers though some of the methods you're seeing on the message boards, I've recently stumbled upon a guaranteed way to find one.
I've been able to get mine from the end of the Crimson Fields, in the War Oni fight. (You can even see in the War Oni's description that his minions are Otomo Couriers.)
Personally, I'd rather spend a little extra time to guarantee finding one; then wandering around 1/3 of Mooshoo looking for a pig wearing darker clothes.
