The Visoreds are a group of rogue Soul Reapers who have "illegally" acquired Hollow powers. The word vizard, a Japanese term meaning "masked warriors" in the Bleach anime and manga, is a play on the English word "visored" which means "masked." Fans of the Bleach anime and manga will often use the term vizard. The current eight known members of the group are as followed: Shinji Hirako, Love Aikawa, Kensei Muguruma, Mashiro Kuna, Rojuro Otoribashi, Hiyori Sarugaki, Hachigen Ushoda, and Lisa Yadomaru. Ichigo Kurosaki by definition is considered a visored, however he chooses not to associate himself with the group.
Being soul reapers who have acquired hollow powers, the visoreds are the inverse of arrancars. They appear entirely human having originally been soul reapers. In order to access their hollow powers, visoreds don a hollow mask. By doing so, visoreds significantly augment their soul reaper powers with hollow powers, as well allow the use of generic hollow abilities and techniques. The nature of their spirit force will also correspondingly change into a a mix of hollow and soul reaper. The visoreds are neither accepted by hollows (for their former status as soul reapers) nor soul reapers and have declared that the only side they're on is their own.
In order to explain some of the roots of the primary conflict in addition to minor ones, Bleach creator Tite Kubo wrote a brief twelve chapter gaiden called Turn Back The Pendulum. In this short flashback story, the visoreds are revealed to have all been soul reaper captains and lieutenants prior to their defection from Soul Society.
 Turn Back The Pendulum
About a 101 years prior to the onset of the main plot, an increasing number of souls living in Rukongai began to mysteriously vanish, leaving behind no traces but the clothes they wore. Captain Kensei Muguruma and his lieutenant Mashiro Kuna of the 9th Division took a team of his subordinates comprising of the 3rd through 6th seats and the division's vanguard to investigate the situation. Sometime into the investigation, the team came under attack by an unknown assailant and were all, including the captain and lieutenant, struck down. The 9th Division vanguard, who were on standby, sent the news back to Captain Commander Shigekuni Yamamoto-Genryuusai, who responded by sending 3rd Division Captain Rojuro Otoribashi, 5th Division Captain Shinji Hirako, 7th Division Captain Love Aikawa and 8th Division Lieutenant Lisa Yadomaru to investigate the so-called mishap. They managed to arrive at the scene in time to save 12th Division Lieutenant Hiyori Sarugaki, who was sent earlier by 12th Division Captain Kisuke Urahara to collect samples, from a hollowified Kensei. The group fought Kensei and a hollowified Mashiro as well, but were overwhelmed despite having greater numbers. Kidou Corps Lieutenant Hachigen Ushoda made a seasonable arrival at the battle site later on and used powerful binding spells to subdue Kensei and Mashiro. Shinji, who was holding onto Hiyori, was unexpectedly attacked by Hiyori who had suddenly formed a hollow mask. Immediately following, Love was struck down by Tousen Kaname, Kensei's 3rd seat and the assailant responsible for cutting the 9th Division's investigation team down. Tousen is shown to have been working for Sosuke Aizen, Hirako's lieutenant, who appeared as well with Gin Ichimaru. Aizen explains that the disappearances that have been occurring, as well as the unforeseen transformations of Kensei, Mashiro, and Hiyori, were all part of his experiment called "hollowification." Shortly after, Rojuro, Lisa, Love, and Hachigen all began to transform into hollows. Declaring his experiment a success, Aizen prepared to kill them, only to be interrupted by Kisuke and Kidou Corps leader Tessai Tsukabishi. Aizen managed to escape, leaving Kisuke and Tessai to take care of the victims. Later that night, Kisuke was arrested and convicted of performing illegal experiments, thus being sentenced to exile into the human world. Shinji, Hiyori, Love, Rojuro, Lisa, and Hachigen were to be treated as hollows and therefore be killed, though Urahara prevented this by taking them with him.
Having a common enemy, the visoreds currently are willing to offer their assistance to Soul Society despite being the victims of the conspiracy 101 years back that landed them where they are now.
 Plot Synopsis
The first of the Visoreds to debut in Bleach is Shinji Hirako, who is introduced as Ichigo's new classmate. One night, he suddenly appears before Ichigo with a zanpakutō, much to Ichigo's bewilderment. Moreover, he forms a hollow mask in his hand and stated that he's a visored, just like Ichigo. Shinji attempted to recruit Ichigo into the visored group, telling him that he doesn't belong with his friends and allies. Nevertheless, Ichigo refused, stating that he is a soul reaper, and left to fight the hollows that were attacking the city.
The following day in class, Shinji appeared again, frustrating Ichigo who forcefully dragged him out of the classroom and demanded why he's still attending school when Ichigo already denied his offer. Shinji replied by saying that he was going to continue badgering Ichigo about it until he accepts, and that Ichigo is already one of them and cannot turn back whether or not he likes it. After their dismissal from school, Orihime and Chad caught Shinji and Hiyori on their way home. They demanded what their purpose and Ichigo's role in it was, but Hiyori hastily refused to divulge any information and threatened to kill them. Alarmed by Hiyori's belligerence, Shinji grabbed her and sped away, telling her not to cause unnecessary conflicts.
After Ichigo, Rukia, and and a group of soul reaper lieutenants and a captain managed to fend off Grimmjow and his Fracción, he decided to visit the Visoreds. Residing in a warehouse surrounded by Hachigen's barrier (which makes everything and everyone inside it invisible and undetectable to the outside), the Visoreds agreed to teach Ichigo how to overcome his inner hollow granted that he pass a test. Initially, they forced Ichigo to use an exercise machine that drains the user's spirit force for three days in order to test how great his spirit force is. Ichigo, growing impatient, declared that he could go for a week straight on the machine before passing out and demanded that he be taught how to suppress his hollow immediately. Knowing how Ichigo quickly attained shikai and then bankai in three days, Shinji agreed to Ichigo's plea. After Ichigo succeeded in defeating his inner hollow and gaining his powers, the Visoreds proceeded to train him so that he could retain his hollow form for longer periods of time. After only about a month of training, Ichigo left to fight a group of arrancars that invaded Karakura Town.
Since then, the Visoreds have stayed in their warehouse preparing for the time of the hougyoku's awakening and Aizen's invasion of Karakura Town with his army of arrancars.
Being a hybrid soul reaper/hollow, visoreds have access to both soul reaper and hollow abilities, which includes the use of a zanpakutou. Tapping into their hollow powers will significantly augment a visored's speed, strength, and abilities available to them. Additionally, while in their hollow form, their rate of recovery is much faster, therefore increasing their endurance as well. Visoreds can also use generic hollow techniques such as cero, which both Shinji and Ichigo have demonstrated. Ichigo, who recently transformed into a new hollow form, has shown the ability to use Sonído, the high-speed movement technique used by hollows.
The possibility of visoreds can be seen early on in the Bleach series when Ichigo began transforming into a hollow before regaining his own soul reaper powers. Ichigo's conflict with his inner hollow is a common symptom of a soul reaper who has hollow powers. The process by which a soul reaper acquires hollow powers is called hollowification. In order to gain full control of their hollow powers, soul reapers must conquer their inner hollow or he/she's soul will be devoured, meaning that there would be nothing stopping them from becoming full hollows.
Being able to don a hollow mask, or hollowify, and retain sanity is a sign that a soul reaper has successfully gone through the hollowification process. However, Ichigo's recent transformation into a new hollow form suggests that this is just the initial stage in the development of a visored's powers.
 Shinji Hirako
Shinji is the first visored to debut in Bleach, and the unofficial leader of the visored group. He is the former captain of the 5th Division with Sōsuke Aizen, his successor, serving as his lieutenant. He's a longtime friend of Hiyori Sarugaki, though their relationship often times becomes very violent.
 Hiyori Sarugaki
Hiyori is a short, blonde haired girl with a feisty attitude and a very short temper. She habitually abuses Shinji (and other men) for often trivial reasons, even when she was still the lieutenant of the 12th Division while he was a captain. When Kisuke Urahara became the 12th Division captain, Hiyori initially held a grudge against him (and abused him) because he was a former member of the Covert Ops, but she eventually developed somewhat of a crush on him.