The former captain of the 9th division,but later retained his position.
Approximately 110 years ago, Kensei was the captain of the with Mashiro serving as his lieutenant. One night Kensei and a few of his squad including Mashiro are sent to investigate strange murders that had been occuring in Rukongai. Mashiro is constantly whining and Kensei physically restrains her. Kensei is then alerted by a Hollow attack, he and his squad engage the hollow in battle.
Kensei releasees his shikai and attacks the hollow which completely obliterates the hollow. He notices a small boy on the ground near him and tries to cheer the crying boy up. He asks the boy his name and the boy tells him that he is Shuhei Hisagi whose family had apparently been killed by a giant hollow. Kensei and his squad then discover the clothing of the missing members, he decides to camp out in order to further investigate.
Later that night while they're resting in the tent they hear a scream, which causes them to run out assess the situation, to see all his men dead on the ground. he sees the killer and knows who it is It's none other than Kaname Tosen who had betrayed Kensei in order to follow Aizen. Sometime later a team of various captains and lieutenants are sent to investigate the disappearance of Kensei's squad. When they arrive they are attacked by two hollows. After battling the hollows for a while, they discover the Hollows are actually Kensei and Mashiro.
With the arrival of Hachi of the Kido Corps, they manage to bind and hold Kensei and Mashiro. The investigation team gathers after the fight and talk about the situation. It within that moment Hiyori starts coughing and becomes Hollowfied herself. It is then they are attacked by Aizen, Gina and Tosen.
All the members of the investigation squad have been used as a guinea pig for Aizen. He had tested the Hogyoku on the captains and lieutenants. He
plans to use the Hogyoku to become an almighty being. The rest of the team start to hollowfy and they pass out. After that Urahara and Tessai find them and bring them to his lab.
The next day Urahara, Tessai and all members of apprehended by the Gotei 13. The members of the investigation ought to be executed, but befor that could happen, Yoruichi gets them out and brings them to an underground hidden lair. After that Urahara, Tessai, and the eight victims escape to the real world, where they would find a way to undo the Hollowfication process
Once Kurosaki Ichigo arrives at the Vizards' base to learn and control his inner hollow. Kensei makes his first appearence. Kensei comments that Ichigo is too scared to learn to control his inner hollow and even going as far to reference his as a "punk" during Ichigo's fight with Shinji.
Kensei is next seen fighting Ichigo in his Hollow form, during the fight Kensei shows his shikai and fires a blast from it. The battle is long and Kensei has to put alo of effort in controlling Ichigo. During the fight he notes that Ichigo heals and hollofies faster than expected. He switches out with Love Aikawa.
He is then seen with the rest of the Vizard arriving at the fake Karakura Town, intercepting Aizen, Gin, and Tōsen's release from Yamamoto's fire prison. When Shinji asks his fellow Vizard if they have anyone in the Gotei 13 whom they want to speak to, Kensei states that he doesn't care. All Vizards don their masks and battle the Gillians. In his battle against the Menos, Kensei brings down scores of them in hand-to-hand combat. After killing the last Gillian, Mashiro complains that she wanted to take the last one, to which Kensei tells her shut up as he is giving her a big one so she should quit complaining. While Mashiro's attention is diverted, Wonderweiss awakens, prompting Kensei to yell at her trying to catch her attention. She tells Kensei not to worry. She overestimates her abilities and undermestimates that of her opponent. She states that she can keep her mask on for 15 hours and thus she can keep her mask on all night. Wonderweiss and Mashiro engage in battle but the Arrancar quickly gains the upper hand when her Hollow mask shatters and falls apart. Wonderweiss takes the opportunity to attack landing brutal punches to Mashiro's face, but before he can continue his hand is stopped by Kensei, who has an unconscious Mashiro in his other arm.
He prepares for battle against Wonderweiss. He then throws Wonderweiss sending him flying. Kensei sets down on a nearby building and lays Mashiro down, and she weakly asks if he was going to avenge her as she tries to smile. He looks down at her asks her what she is smiling at, noting she is a dumbass for ending up the way she is and how she could have avoided if she had listened to his warnings. He then takes his Shikai out of his pants pocket and states that he is going to give that annoying little kid a taste of his fists, not to avenge Mashiro, but instead because the brat got above himself. As Wonderweiss approaches him, Kensei releases his Bankai and the two battle resulting in a huge explosion.
As a former captain, Kensei has mastery over swordsmanship, shunpo, kido magic and martial arts. Besides his teachings Kensei also posseses enhanced strength and immense spiritual power. Like all Shinigami Kensei has a Zanpakutō.
Tachikaze (lit Earth-Severing Wind): When sealed, it is shown as a short katana with a rectangular guard in an 'H' shape and white hilt weaving.