Can be augmented by Oboro after obtaining KI "Scintillating Rhapsody" gained from completing RoV missions. Speak to him first about it and then trade him the weapon with either a Beitetsu, Riftborn Boulder or Pluton. After confirming your decision trade him more of the same item you gave him originally with the weapon to increase augments - it takes 299 pieces to max and there is only one upgrade path regardless of the stones you use.
When fully augmented will have:
Pet: Accuracy +70
Pet: Attack +70
Pet: Double Attack +15