Arc 4The Arrancar Army
Rei fought the Quincy, confronted Kōga, and built an army in Hueco Mundo after helping Grimmjow’s group defeat Baraggan’s forces. The arc left Rei investigating the army’s captured scientists and their experiments while Aizen began pursuing power and reform.
- Haschwalth used The Balance to turn Rei’s injuries against him, but Rei restored himself, released Bankai, and drove Haschwalth to flee into the Shadow Domain.
- Rei led the Soul Reapers’ campaign against the Quincy and later judged Kōga’s captaincy prospects before Kōga was framed, sentenced to Muken, and stripped of Muramasa.
- Rei defeated Kiganjō, then joined the fight against the Hollows and entered Hueco Mundo to aid Grimmjow’s group against Baraggan’s forces.
- Rei’s side defeated Baraggan’s forces at Las Noches, though Baraggan, Szayelaporro, and Picaro escaped through a Garganta.
- Rei formed the Arrancar Army, put Ulquiorra in command, and brought Ashido back to Soul Society after persuading him to leave Hueco Mundo.
- Rei returned to Seireitei without punishment, and Ashido reclaimed his former seat in the 11th Division.
- Ten years later, Aizen concealed his captain-level strength and began considering how to gain power to pursue reform.
- Rei investigated reports of Hollow attacks and learned that scientists in Hueco Mundo were studying soul bodies and Reiryoku, then went to observe Ulquiorra’s test subjects.