InuYasha: The Final Act

Sango's Feelings, Miroku's Resolve (1x12)

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During a new moon, Sango and Miroku face off against a Bone-collecting demon. During the battle, Miroku is forced to use his wind tunnel twice, resulting in him becoming poisoned. To protect him, Sango coats Hiraikotsu in poison and uses it to destroy the demon, destroying her weapon in the process. Myouga suggests they visit the Demon Potions Master to have it repaired. The drunken man agrees to repair it and dumps it in a jug of alcohol, dissolving it. He sends Sango into another jug to pacify the demons inside. The demon's are the Hiraikotsu which want Sango to promise not to betray them again, but she refuses, saying that as she loves Miroku, she would sacrifice her life for him. Outside the jar, the Master of Potions offers Miroku a poisonous drink that will prevent him from feeling the pain of any other poison or demon miasma, though it will not actually prevent it from reaching his heart. Hiraikotsu initially intends to kill Sango, but Miroku drinks the poison so he can continue to protect Sango. The Hiraikotsu demons agree to fight with her once again, and Sango's weapon is fully restored, and is now much stronger and much more powerful than ever before.