So, just did this and was successful. 1/1
After reading the rest of these posts, I grabbed as many pamamas as I could and hopped a chocobo over to the Teardrop Spring where I found the ???. After trading about six stacks of pamamas to the ???, I got him to pop. After a reletively lengthy fight for a lvl 75 MNK, I was ecstatic to see that he dropped the Nanban Kariginu.
But the most important thing with this fight is to bring as many pamamas as you can. Even if you don't use them all, you can still eat them to bring out the armor's hidden effects.
All-in-all, I thought it was a good quest. Easy to pop, if maybe a bit expensive. Easy to win for a lvl 75. Seems to be a pretty good drop rate too. Good luck, everyone!