Delta

Hiiro Ōkoku (緋色王国, Scarlet Kingdom) was an arrancar from the original espada team, along side Aaroniero Arruruerie, having the title of noveno (9th) Espada before she was demoted and he was placed in her spot. She always hated Aizen for what he did and vowed to end his life if it was the last thing she could do.

Early years
Hiiro was an adjuchas-class Menos prior to shinigamification. She was a member of the the Espada prior to its current membership, being ranked noveno (9th), prior to her demotion and being replaced by Aaroniero Arruruerie. She was the first female arrancar created artificially after the demotion of Privaron Espada Cirucci Sanderwicci but before Nelliel Tu Odelschwanck and Tia Harribel were converted to arrancar. Unlike her replacement her aspect of death wasn't greed, it was Despair.

Demotion
After the advancement of Aizens experiments, Hiiro was demoted to a numeros and replaced by Aaroniero Arruruerie, much to her anger. This led to her abandonment of post and the destruction of her chamber in Las Noches.

Powers and abilities
Master Swordsmanship Specialist: As a former Espada, Hiiro has much experience at fighting, showing hardly any effort in her advanced use of swordsmanship. Her body flows elegantly when engaging in combat, so finely tuned that she can stop her attacks at a moment's notice and subsequently execute lethal attacks with absolute precision.

Sonído Master:

Hierro:

Cero:

Zanpakutō
Dākukoa (ダークコア, Dark core): Her Zanpakutō is a katana with purple wrappings on the hilt, and an ovular crossguard.