Hollow Ichigo was born from the special Hollow that had been created by Sosuke Aizen by folding thousands of Soul Reaper souls. What he created was a Hollow he called White. Just before White was destroyed by Masaski Kurosaki, he had infected her. This Hollow spirit was later passed on to Masaki's son Ichigo, and merged with his latent Soul Reaper powers to become his zanpakutō, Zangetsu. However, Ywhach, the spiritual embodiment of Ichigo's inherited Quincy powers, has been impersonating Zangetsu and holding back Ichigo's true abilities.
Hollow Ichigo (虚(ホロウ) 一護, Horō Ichigo) is a supporting character of the BLEACH series that was created by Tite Kubo, It first began serialization in Shueisha's Weekly Shonen Jump in August 2001. He was first introduced during the Soul Society: The Rescue Arc that began in Volume ??.
He first appeared in BLEACH Volume 13 CH. 110 "Dark Side of Universe".
Throughout much of the BLEACH series, Hollow Ichigo was thought to have been a side effect of Urahara artificially rebooting Ichigo's Soul Reaper powers. It wasn't until the final arc of the series that it was revealed that Hollow Ichigo is in fact the true spiritual embodiment of Zangetsu.
Major Story Arcs
Soul Society: The Rescue Arc
Through many of Ichigo's battles in the Soul Society, his life was saved by the intervention of Hollow Ichigo. He had asserted himself through the Hollow mask to block what would have been lethal strikes, and Ichigo was completely unaware of this. What was until his fight with Zaraki Kenpachi. Before Ichigo died from his wounds, the spirit of Ywhach pulled Ichigo's spirit into the inner world and unleashed Hollow Ichigo on him. Ichigo was forced to battle Hollow Ichigo to prove he was worthy of wielding Zangetsu. In their fight, Hollow Ichigo showed the real Ichigo how Zangetsu was designed to be used, but Ichigo managed to turn the tables and regain control of Zangetsu. Hollow Ichigo was then resealed by Ywhach.
During Ichigo's later battle against Byakuya Kuchiki, Hollow ichigo managed to overtake Ichigo's personality and form the Hollow mask. He was nearly ready to over power and defeat Byakuya until Ichigo fought back to regain control of his own body.
Out of fear of Hollow Ichigo's growing control and influence after the appearance of the Arrancar, Ichigo joined the Visored to try and tame Hollow Ichigo to obtain the ability of Hollowfication. During the training, Hollow Ichigo and the real one confronted each other once more in the inner world. Hollow Ichigo announced that he was Zangetsu as he fought Ichigo with a white version of the Zangetsu sword in bankai form. Hollow Ichigo nearly overtook the real one in their battle, but Ichigo turned the tables back on him once more in thei fight for King of the Hill. With Ichigo's victory, he had the ability of Hollowficaiton to draw out the Hollow powers within to augment his current abilities.
Ichigo took these abilities into the Hueco Mundo to rescue Inoue Orihime.
Fake Karakura Town Arc
As Ichigo seemed dead at the hands of Ulquiorra Cifer, Ichigo tapped deeper into Hollow Ichigo's powers that he ever had before. In this state, Ichigo had seemingly no control as he fought once more with Ulquiorra. He was more like a mad beast of a hollow, but with incredible powers.
Before Ichigo was to have his final battle with Sosuke Aizen, Ichigo returned to the inner world to face with Hollow Ichigo once more. He had been drawn out of Ichigo by spiritual embodiment of Tensa Zangetsu. Hollow Ichigo took on the appearance of Ichigo's Hollow form mask. Hollow Ichigo and Tensa Zangetsu merged together to battle Ichigo in his attempt to obtain the power of the Final Getsuga Tensho. He won this not by fighting, but by surrendering himself. Using the Final Getsuga Tensho would mean losing his Soul Reaper powers. With tears, the merged spirit lamented that he'd no longer be able to protect Ichigo.
The Thousand-Year Blood War Arc
Powers & Abilities