Marry any of the girls then save your game. When you turn on your game again, you should see that the Sharance Tree is in bloom with a new voice actor singing the song and new scenes.
This glitch can only be done after you beat the first dungeon (the Forest),and requires a second player with another copy of Rune Factory 3:
Steps:
1. Save your game
2. Enter into the multiplayer dungeon (any field)
3. Give the other person the items you want to duplicate
4. Exit and reset without saving
You and the other person should now both have the items exchanged in Step 4.