Bleach Chapter 676

After greeting a shocked Orihime, Ichigo confirms Yhwach's assessment that this is the form he takes on when melding with his Hollow powers before explaining how he reforged his Zanpakutō after his Hollow and Quincy powers came into balance with one another. 

Noting that they should logically come forth if that balance is disrupted, Ichigo states that his Hollow powers have always come forth when he exerted his Shinigami powers before revealing that he had to draw them out with the help of Yhwach's power. As Yhwach grins at this, Ichigo moves in front of Santen Kesshun while telling Orihime to keep up her guard before unleashing his Reiatsu, which destroys most of the room around them. 

Yhwach commends Ichigo's power and forms his broadsword, only for Ichigo to grab him before slashing at close range. However, as more of the tower is destroyed by the force of the attack, Yhwach blocks Ichigo's blade with his bare hand and claims that he could not be harmed by Ichigo's level of strength before tossing him back. However, Ichigo proceeds to form a Getsuga Tenshō and fuse it with a Gran Rey Cero before firing it at Yhwach, who is cut deeply.