When her husband betrays her, she starts convincing herself that betrayal can be a proof of love, using up all of her tremendous vitality in doing so. Indeed, she in turn betrays him, just to demonstrate this point, to herself mostly, but also to him. And then later on, when she is betrayed by him for a second and final time, she has reached the point of absolute certainty. Betrayal not only proves love, she knows, but is equivalent to it: the more total the betrayal, the deeper the love. Him possibly forging his own death certificate so that she cannot even mourn him is the ultimate act of devotion. Happily, she glides into madness.
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Kurosawa applying his uncertainty…