After the event in which you obtain the Red Ring, talk to a man that is in the shop next to the bar. He will give you chalk. Trade this with Ekei to get a book. Trade the book with Magoichi to get an emblem. Finally, give this to Kotaro in return for a melon. Take the melon to the man. After you rescue Oyu from Gifu Castle, talk to the man's father, who is standing next to him. He will give you a special necklace.
After you rescue Oyu from Gifu Castle, this will be your final opportunity to buy items and receive gold from enemies. Your goal is to clean out the store next to the bar. After this is accomplished, talk to the salesman again, and he will give you a special necklace.
Unlock Hard mode=Complete the game on normal
Easy gold and souls=On the path before the gold mine, you will be attacked by a number of Nobunaga's guards, kill them and pick up the gold and souls they drop, you can repeat it.
Obtaining the healing Stone=If you find yourself with an absolute abundance of gold, buy all the items in the shop at the town, Once you have completed the hefty transaction, talk to the shop keeper again and you will recieve the healing stone.