The Forgotten City (JP)

This wasn't working for me when stealing the medicine but this method I found worked for me:

As soon as you go down the stairs from the beginning area, go into the tavern on your left:


Once inside, look to your right to find this room next to the stairs:


Inside this room is a chest with some Gold you can steal. Once you steal it, the Golden Rule will activate. Now just go back up the stairs you came from and go through the portal that is activated by Sentius (after waiting up there he'll come eventually). After you go through the time portal just steal the gold again and go back to the portal (once Sentius arrives and makes it). Repeat this process of stealing the gold and going into the time portal 3 more times to unlock the achievement!