Bleach: Beyond Good and Evil

gamerant.com:

It would be a mistake to think that Ichigo from Bleach is just another anime protagonist who has to conquer and defeat an evil version of himself because that is not what he is doing when he fights the spirit of his Zanpakuto: Zangetsu. While Zangetsu may first appear to be an agent of evil hellbent on making Ichigo's life more difficult, he is in reality a balancing force there to help Ichigo become stronger.

There is a reason why many Bleach fans mistake Zangetsu for an evil Ichigo: He is destructive, psychotic, and he looks exactly like Ichigo aside from his coloring. Indeed, when doing a side by side comparison with Ichigo and Zangetsu the two of them could be the two halves of the Ancient Daoist symbol of the Taijitu (yinyang). The visual reference immediately suggests that the two are what a Daoist would call a pair of inseparable and contradictory opposites (i.e. male and female, dark and light etc.).

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To further bolster the claim that Ichigo and Zangetsu are inseparable and contradictory opposites, it is important to understand what the function of their relationship was in Bleach's overall story. Zangetsu first appears after Ichigo gets beaten to a bloody pulp by one of the strongest fighters in the series: Kenpachi Zaraki.

The reason why Ichigo loses the fight initially is that he is paralyzed by fear, and refuses to accept help from Zangetsu. As Ichigo drifts in and out of consciousness he is dragged into his inner world, where Zangetsu is waiting to challenge Ichigo for the right to control his body. Zangetsu fights like a wild animal, in contrast to Ichigo's defensive style. He bullies Ichigo, taunts him, and exposes how little he understands about