Uh wish I could help you there, but I haven't gotten that far yet since I've restarted.
I'm a little stuck myself actually, I'm trying to get the orichalcum in the quest chain to obtain the Sword of the Valiant (or something like that) and I'm just... lost.
For those who don't know what I'm talking about, the above sword is one of the Hero Equips you can obtain, and is probably the most annoying to get. You start off in Miore, go to the well at night with 100+ lewdness and let the old guy bury himself in your breasts, he'll give you a brooch.
As it turns out, that brooch was what the rich guy in Port Gar was looking for, give it to him and he'll give you a Diamond. Go to the Desert Bazaar. You'll need to have sex with the guard blocking the way to the stairwell. Once he's out of the way go down and open the cell with the Last Key and talk to the Nun. Give her the Diamond and the the child next to her will vanish, use the pickaxe to obtain an ammonite fossil. Take the fossil to the guy who will sell you increasingly expensive things (capping out at 10k), he'll trade you a vibrator for it.
Go to the forest village at night, give the vibrator to your exhibitionist nun friend and she'll forever be your bestest friend in the world and will also give you an Abnormal Book. Teleport to Rinne or Karai and sail north until you reach the well with all the books. Go to the left most bookshelves, the man will stop you, but will let you proceed. Obtain the memo.
And here's where I'm lost. The memo will lead you to the first floor of the tower where you got the first two keys from. (It'll have the huge face pattern on it).
From what I could get from google translate, apparently I'm supposed to mine the left cheek or something... Then from a pillar in the northeast, go east 4, north 6, west 2... But unfortunately, no results. If anyone has gotten the sword, could they tell me how to proceed from here? In the meantime I'll continue to try to figure it out :x.
EDIT: HAHAHA. Figured it out a minute after I was complaining. When the memo means left, it's from the perspective of the face its referring to. So from our top-down perspective, it would be the right cheek. So head to the right cheek, at the very back middle of it (You'll know it by the farthest set of carved tiles) there will be a hidden staircase, go down it and you'll end up in a room with four pillars. Go to the bottom of the northeastern pillar then head right 4, up 6, left 2. There will be another hidden staircase on the tile you end up standing on. Go down those stairs and open up the cell with your Last Key and obtain the orichalcum!
