Ryusei Kenzaki

Ryusei Kenzaki is the little brother of Hokuto Kenzaki coming from a lineage of swordsmith and the uncle of Touka Kenzaki who he trained soon after the death of her mother. He is also the one who trained Hayato in swordsmanship as a child.

Appearance
Ryusei is shown to be an older male with long black hair that he has tied in the back and hazel colored eyes, as well as a far muscular build. He is first seen to be dressed in a martial art uniform that has no sleeves.

Personality
Ryusei first comes off as a respectful man as Hayato trained with him in the Kenzaki Dojo after the First Attack. But, he is also a lazy man who doesn't clean up his own home and even leaves cleaning it up to his two disciples, which caused others to not join his dojo as parents don't trust him with training their children. He has also been noted to be quiet perceptive which is the reason why he didn't want to bring Emilia (knowing that she would have followed him) since Ryusei would've deduced that she wasn't a male student.

The other reason that Hayato didn't visit with Emilia was that he is perverted towards women reaching adulthood, which is a bad choice as Emilia, Sakura, Karen, and Miharu who are all mostly composed of woman in their adulthood. It can also extend towards his niece who Ryusei had shown some restraint with, but due to Touka reminding him far more of her beautiful mother instead of his brother and would've reached his limit and "attacked" her if Hayato hadn't agreed to take her to Little Garden to train.

History
Both Ryusei and his older brother, Hokuto were close to one another the moment they held swords in their hands as blood brothers who comes from a long lineage of swordsmith, which has spanned for at least a thousand years. He practiced with his older brother using bamboo swords every day around their home with Ryusei losing all the time until he turned ten-years-old and continued to win ever since.

Soon after the savage started to attack, Ryusei was the next one chosen to wield the sword that his brother forged utilizing a variable stone as raw material. Though even his attacks in wielding the sword could barely affect them until the creation of his Zaneizan. Ryusei soon retired from fighting against the savage after being influenced by their virus causing him not to move like before and even received a serious wound.

Years later, after the Second Attack, Ryusei met Hayato who wanted to train under him to become strong enough to protect those important to him, which he agreed to. Before he starting official training, Ryusei always made the young Hayato clean up around his house. Soon enough, he had him enter a Kendo Tournament in middle school, then watched as his disciple won it.

Powers and Abilities
Enhanced Condition: He is much stronger compared to even grown adults, as he alone could hold and wield the heavy sword that his brother made and fought against the savage for years despite not being a slayer with sense energy. Ryusei was soon forced to retire after being infected by the savage virus.

Master Swordsman: He is a master swordsman who trained in the Kenzaki Dojo and was viewed even as being a genius able to defeat adults at the age of ten, as shown as he was able to even defeat a couple of savages in the past upon reaching adulthood. Ryusei also later trained both Hayato and Touka in swordsmanship.
 * Zaneizan ( 残影斬, Tracing Slash ): A secret sword technique that he created, which uses natural vibrations, in the initial strike and amplifies it more than three times in the second strike, letting Ryusei break through the densest of materials, even the steel-like shells of the savages without energy.

Equipment
Unnamed Sword: Ryusei is in possession of a pitch-black sword his brother forged using a variable stone as raw material, which had proved too heavy for other adult males to wield. Unlike other weapons like missiles and guns, it is a sword able to dent the shells of savages, but before the creation of his secret technique, it couldn't kill them.

Second Unnamed Sword: Ryusei carried another version of the sword made using by variable stones, which his older brother used until his death and handed it off to his niece.

Trivia

 * His first name Ryūsei (流星), which means "Meteor" and "Shooting Star".
 * Her surname Kenzaki (剣崎) means "Sword Peninsula".