Yeah, he's in the alchemy shop in the city. He's there 10% of the time - there's a random number generator 1-10, and he's there when the number is greater than 9. He's in a purple robe. He's got two tiers of sales - you gotta go through the first scene to unlock the entire sale inventory.
Thanks so much!
No worries! There's also two scenes with the weapon shop owner. Give him five "weapon polishings" to get the second scene.
Well, I've only gotten to it once, but basically you need to collect "good end keys", which you obtain by going through bad ends. The way I did it was first doing Sifu's bad end, and then Banka's bad end, and then Iburu's bad end, after which Umi gets an opportunity to repent and try for the good end.