-( Story related, cannot be missed )-
While running through the castle of Oni Island, you will actually come across some of the warning signs that this is where you will get this brush technique: by that, I mean the lightning boxes. In fact, some of the pathways you'll go through will actually involve electricity as an element, so when you get further ahead, you'll find a statue with a bow on its back, aiming towards the storm on the horizon.