In the events of the arc, the one who acts as Ichigo's Zanpakutou spirit is White Zangetsu, back then known as Hollow Ichigo.

Masakazu Morita was spotted posing with the Proplica of Ichigo Kurosaki’s sword Tensa Zangetsu from Bleach. The Japanese voice actor who performed as the series’ protagonist found the replica ...

This is believed to be a sign of their extraordinary power. The only other dual-wield Zanpakutou is Ichigo's Zangetsu, each blade representing his Hollow and Quincy sides. Something about the ...