Orochi will be protected by a barrier, making all your attacks not do any damage. You should be able to evade the slow moving flames on the fire head. Later, use the Waterspout Brush to pour the sake into the Orochi's mouth. Do this two times and one of the Orochi heads will get drunk. Walk onto the Orochi's neck and reach the bell, then attack it until the bell's health gauge reaches zero. The barrier will shatter and you must get the all the Orochi heads drunk. Do the poison and darkness head last. You are now able to attack the heads when they are drunk with your weapon (preferably the Beads of Life) and brushes. Continue until Orochi is defeated. At the end of the fight, Susano will appear. Use the Power Slash Brush wherever the kanji (Japanese symbol) is, and the Orochi is defeated.