Ep. 39: Ichigo enters Zangetsu's world to understand his zanpakutou's true nature.

39

Zangetsu, the spirit of Ichigo's zanpakutou, transports Ichigo into his inner world. There, Ichigo battles a hollow version of himself, leading him to realize that zanpakutou are more than simple tools and that merely knowing their name does not grant power. This newfound understanding allows Ichigo to fight Kenpachi on equal footing. As the two warriors clash in a massive strike, Ichigo collapses. This segment is part of the Soul Society: The Sneak Entry arc, specifically episode 19 out of 21.