Gion Blacksmith is the shop of the blacksmith known as Tamsoft in Cyberdimension Neptunia: 4 Goddesses Online. By offering the required materials and money, you can strengthen your weapons and armor.
You can acquire materials from Material Acquisition Points or Treasure Chests in dungeons. They can also be acquired via defeated enemies.
By strengthening weapons and armor, their parameters will increase. The upper limit to the number of times you can strengthen something is dependent on its type.