Kii is very tall and thin man with long arms and legs and a rather lanky figure. He wears a dark suit similar to Lugh's and has dark eyes and pale skin, along with very silky hair pointing upwards. He has rather dark lips. He carries his sword on his back in a dark black scabbard with a dark strap across his chest. After losing Setsunamaru, Kii began carrying wooden practice swords with him as temporary replacements and still wore his strap to add on to the illusion of still having his weapon. After gaining his gardening hoe from Shigure Kosaka, Kii stopped wearing his strap altogether and began carrying his hoe with him everywhere.
Kii is introduced as a master who is rather careless in his skills, as he cuts down one of his own allies reflexively and unconsciously while he meets with them to hunt for Shigure Kosaka. To compensate for this, he gives out instructions for dealing with him, amongst them to never point a sword at him, never insult him and to stay three meters away from him. He is quite courteous to both his allies and enemies, however, and he tends to become very excited in the middle of a fight
After Shigure takes Setsunamaru from him, Kii becomes extremely underconfident in himself, reduced to cowering in his shack while birds built a nest in his hair. This extends to his honor as well, as he openly begged (and cried) Shigure to give him back the sword without any regard for his dignity.
Kii holds Setsunamaru dear to himself, likely because any other blade he uses quickly breaks from his power. His love for swords extends to a disinterest in women, whose faces he is never able to remember (he only remembers Mikumo Kushinada after recognizing her techniques). In fact, he has to be reminded of Shigure's name sometimes, as he refers to her as "Mic-chan". He will use other swords if deemed necessary but will feel no connection with the weapon, though when he does use the Akabanetou, he proclaims his realization of momentary love for the new sword and cries for Setsunamaru to forgive him for his infidelity.
Since having gained the Hoe from Shigure, Kii willingly left Yami and took a turn in life, as he became much more kinder and thoughtful, having no longer hold any ill will to Shigure or Ryozanpaku anymore and now lives a humble life of peace. He's also grown fond of farming, having used his new weapon for farming purposes such as cultivating plants and caring for livestock. He's also grown to care for Shigure now, as he willingly allied with Ryozanpaku to help save her and was more than willing to fight his former Yami allies to save her. However, he is willing to kill them, suggesting he may retain some of his Satsujinken beliefs (though he said it in a comedic manner, suggesting it was just him losing his temper).
Another thing to note is, after receiving the hoe from Shigure he came upon an injured bird next to him on the ground, put it back on the tree and started to care for them until one day he saw one of the injured birds and when he went to the next he noticed that the nest is empty and a snake just finished devouring them. He realized that in some ways he was the snake that hurt and ruined many lives and he felt overwhelmed with guilt claiming that he is beyond forgiveness but he still wants to give his life to save Katsujinkens and the pride of Satsujikens which he did since he saved Akisames life and was able to help ONSF realize that even if they are Satsujinken they should have some pride and honor as martial artists.
He has a habit of saying "Nyo" when he gets riled up.
- Master Swordsman: Kii is a sword master who is able to attack and re-sheath his sword without appearing to move (getting the nickname Otokoeiaigiri (Japanese for "Supersonic Iai Slash") and is also double-jointed, which gives him the ability to attack people behind him as easily as if they were in front of him. Kii's ability to un-sheath and re-sheath his sword is incredibly fast and instinctive, so instinctive that he has developed the ability to automatically cut everything that approaches him with his Iai draw, and to instinctively cut down anyone who either points their weapons at him, upsets/insults him, or does not follow the rules of his personal guidebook. After losing Setsunamaru, he has shown to be able to not only perform his Iai draw with a wooden sword, but is even able to perform it with other tools like a hoe. He is considered to be an incrediblely high-leveled sword master, as he has reached the highest level of swordsmanship, "Shinto Kourenzan" which is the mental state were the user and his sword become one.
- Expert Gardener: Ever since he lost his Setsunamaru, Kii has received a special hoe from Shigure, which according to her is one of her father's "masterpieces". After recieving it, he tested it on the front grounds of his property, and instantly fell in love with the feeling of using his techniques with it, which he described as "Iai against the Earth". Ever since then, Kii has started a massive garden on his property and has become a expert in gardening.
- Immense Sei Ki: Kii has been shown to have a large amount of ki, which was evidenced by the size and range of his Seikuken. The range of his Seikuken is enormous, easily including Kenichi who was standing several feet away from him, and extends even further than that, due to his enormous height and his sword, a hitogiri bouchou and nodachi.
- Immense Speed: As an Iaido master, Kii has been shown to have an unbelieveable amount of speed and skill with swords, and this speed is both a blessing and a curse to him. His speed and skills are so great that normal swords simply break down from his techniques, unable to withstand them. As a result, he has a hard time finding swords that he can actually use in battle and he only feels a connection with Setsunamaru, the hitogiri bouchou he received from Shigure's father when Shigure was still an unnamed child, and a sword which is able to withstand his enormous techniques. Since losing Setsunamaru, Kii has found a new weapon which is strong enough to handle his techniques, and has begun to create a connection with his new hoe. During his fight in the Eternal Sunset, Kii was capable of running in a circle clearing all of Mildred's arrows with his Hoe even after being pierced all over his body by arrows.
- Immense Endurance: While as thin as Kii is, he's shown to have an incredible amount of durability, having taken a direct attack from Mikumo and recover in mere moments. Even after having his body skewered by arrows from Mildred, Kii was able to still plow all of her arrows before falling from exhaustion from his injuries. Despite his heavy injuries, Kii was still able to rise back up and endure being impaled by multiple blades and seemingly would have still been able to fight had he not been killed by Mikumo. She acknowledged Kii as man with a strong life force.
- Master Unarmed Combatant: Kii has shown that even without a weapon he can still be formidble, this was evident when he caught the axe masters' axe strikes with his bare hands to save Kenichis life as well as more recently being able to almost KO and gravely damage Seitarō Raigo despite the earlier injuries he recieved from Mildred, Kushinada and a sneak attack from Seitarō. It should be noted prior to Kii's punch, Seitarō had not recieved any injuries as well as being fresh in the fight but after the punch his sunglasses ended up breaking and he was visibly shaken up and has been damaged a great deal.
During Shigure's childhood, Kagerō Kii is seen walking out of her father's shack, admiring the new sword he received. Yearning to test out the new sword, he sliced a bird in half prompting the then unnamed Shigure to attack him; but quickly dodges the attack. Were it not for Hachirobe's insistence that Kii leave immediately, he would have killed her. Before he left, he told her that she had to wait a few years for what awaited her next, leaving a shadow in her heart which she describes as her "trauma".
During his fight against Shigure, he stated that he killed people to improve his skills and that's the only way he knew how to improve as a swordsmen.
In should be noted before giving his life to save Akisame's, he stated that he has killed many people because he was born as a satsujinken, and killing was all he knew and had lacked the moral guidance to know any better since during his fight against Shigure, he stated that he killedy people to improve his skills as a swordsmen and that's the only way he felt could do so effectively.
Yami/YOMI SagaEditMikumo). While he does manage to cut her overcoat, he is unable to lay a scratch on her as she deflects the sword with only her bare hands. The fight carries on to inside a nearby building, where he manages to cause some injuries to Shigure, who cuts his wildly spiking hair and continues to insult him with the words "sea urchin" and "flatfish face". Kii knocks an attacking Tōchūmaru into a pillar, angering Shigure and prompting her to use the cutting edge of her sword against him, defeating him and making him realize Shigure's true identity, noting that that is the reason why his Setsunamaru refuses to cut her. He falls, still grasping his sword, which Shigure takes forcefully from his grip. Chikage, on an errand for the Akabanetou so that Chikage may witness weapon combat. He is seen curling up in his large shack, depressed to the extent that birds made a nest out of his hair (an ironic note, considering that he killed Shigure's first friend, who was also a bird) and with broken swords laying about him. Again unable to recognize Mikumo, Sai takes up her offer for one of the Akabanetou, a new sword he could use that would endure his strength. During the Battle for Akabanetou, Kii is brought to Kenichi by Mikumo, and promptly clings to his legs begging for Setsunamaru back. He then grabs Kenichi and rushes to the site of the Akabanetou, during which he retrieves one of the swords and tests it out, easily slicing through a fellow weapon-user's weapons. However, this does not satisfy him, as he claims that "there is no chemistry between us", and then begs Shigure for Setsunamaru back. He turns on his compatriots when he accepts Shigure's offer to give him a weapon if he protects Kenichi, becoming successful in doing so.
In the aftermath, Shigure gives him a hoe made by her father that "matched his feelings the most". After some initial tension, he grabs the Hoe and runs outside, cleaving the earth happily with his new weapon. It is noted afterwards by Shigure that Setsunamaru wants to return to him as well, to which she replies "One day, you will ...".Shinpaku Alliance and Yomi, Shigure pays a visit to Kii along with Apachai, Kenichi and Miu. Shigure asks if he gathered the "stuff" for her, to which he did, as it was revealed to be bags of dirt and a device for extracting iron sand from the dirt and sand she gathered. The purpose of this was for Shigure to forge the iron sand into metal, which she can use to provide arms for the Shinpaku Alliance. He and Apachai were seen forging metal very wildly to the point Kenichi and Miu left out of fear of what they could do.
Later he is seen with Akisame Koetsuji, Shio Sakaki, Apachai Hopachai, Kensei Ma, James Shiba, and Danki Kugatachi rescuing Shigure Kosaka. He helps engage battle against the military while noting he can finally hear himself think. When Mildred attempts to kill Danki with an arrow, Kii saves him and later is confronted with the rest of Ryozanpaku to the Yami and Hachiou members present. After Ryozanpaku makes the first move, Kii engages battle noting play time has come for them.
He was seen engaging battle against Rin, agreeing to watch Danki's back. Rin, who is fighting with Kagerō, asks why he has switched sides. Kagerō explains that because of the hoe Shigure has given him, he has realized he does not dislike the peaceful ground and has come to emulate the feelings contained in the hoe. He adds that Shigure cannot die until she has given his sword Setsunamaru back to him and goes on the offense. He then almost deals a wound to Mikumo when she takes her eyes of him for a moment, to which Sai warns her not to.After Mildred recovers her bow, she unleashes a furry of arrows, as Mildred focuses her eyes and shoots at the Katsujinken masters directly, forcing them to dodge Mildred's strikes along with the falling arrows.
Kagerō Kii and Mikumo are fighting and Mikumo announces that the time for their defeat has come as she produces multiple clones and surrounds Kagerō. Kagerō unleashes his secret technique but Mikumo evades it, appearing behind Kagerō and slamming him into the ground.
Just as Mildred is about to attack with her Double Pupil Bow: Writhing Hedgehog, a voice is heard coming from the ground and it revealed to be Kagerō. He has recovered thanks to "the earthworms and the crickets cheering [him] on" to defeat Mildred for all the arrows she has struck into the earth. Mildred aims her bow at Kagerō but he stands and uses Hidden Sword Technique: Otogoe no Tenchigaeshi, running in circles around the battlefield and clearing it of arrows.Mildred aims her Writhing Hedgehog at Kagerō and the attack connects, causing him to stagger and to let go of his weapon. Despite the damage Kagerō reclaims his weapon and completes his technique, clearing the battlefield of arrows. Kagerō then falls uncounsious after an attack from Seitaro Raigou. When Hayato Furinji calls all martial artist that follow their beliefs as martial artist, Kagerō heard the message and wakes up. Just as Akisame is trapped between arms and Seitaro is about to deliver the finishing blow, Kii intercepts the attack and punches Seitarō in the face, breaking his sunglasses. Kii begins to prepare an attack meanwhile remembers his previous life as a Satsujinken martial artist, but states that he will give his life for helping Katsujinken fighters and Satsukinken fighters' pride. Just then, Mikumo rips apart Kagerō Kii, killing him definitively.
- He bears a resemblance to Edward Scissorhands from the movie of the same name.
- He also resembles Dream of The Endless from the Sandman comic book series.
- He is the first character to have been in Yami and left to have allied with Ryozanpaku.
- He is the second Ryozanpaku´s ally to be killed by a Satsujinken martial artist/Yami member, the first was Tsutomu Tanaka (killed by Ogata Isshinsai), Kii was killed by Mikumo Kushinada.
- Despite being able to fight on par with the strongest members of Yami, it was never stated why he was not a member of the Hachiou Executioner Blade. With the only explanation could be because to be a member of OSNF or a member of the Executioner Blade you may need to have a disciple representing your style which Kagerō Kii was not known to have a disciple at any point in time.
- vs Shigure Kosaka (interrupted by her father, though he states that she would have lost)
- vs Shigure Kōsaka (Loss)
- vs Yami Axe User (Won)
- vs Rin Tachibana, Mildred Lawrence, Mikumo Kushinada & Seitarō Raigō (Lost)
- vs Mikumo Kushinada (was killed)