Once you get the Four Sword, go to the Inn and go where the three girls are. Go up to Din, (red hair) and fuse kinstones with her. It should show the guy named "Gorman" going up to the locked house, saying he wants to rent it out. Go talk to him, and decide witch Goddess you want to give you a charm. Whatever one, go talk to her, and she goes to live in the house. Go talk to her in there, and she gives you a charm for your empty bottle.