In the manga and video game, Koganei has blue hair and blue eyes. He wears a white T-shirt with a vest over it, as well as shorts and sneakers. He wears different sorts of street clothes throughout the rest of the manga. Under a bandanna he wears tied around his right wrist is a suicide scar.
In the anime, he has brown hair and eyes, he wears a necklace with the similar color to Kogun Anki, and an attire similar to the manga and game.
Little is known of his early life, but given that in a manga flashback Kaoru was seen attempting to commit suicide, it can be assumed he was a lonely child until he met Kurei. Kaoru is the youngest member of Hokage, and as such, his personality reflects his age. Even in battle, Kaoru is playful, and sometimes has a tendency to toy with his opponents as if the battle were a game.
Part in Story
Kurei's Mansion Arc
He first appears to kidnap Yanagi, alongside Mokuren. After successfully doing so, he holds guard at Kurei's mansion, later fighting Tokiya Mikagami (the two of them gain a lot of respect for each other's respective skills following this battle).
In the anime after his battle against Tokiya, Koganei assists Ganko to save Fumio Tatesako after Recca and his friends rescues Yanagi at Kurei's mansion. He later defects Uruha after realizing that Kurei hurts Yanagi due to her healing powers.
Ura Butou Satsujin
Before the fight between Team Hokage and Team Uruha Maboroshi, Koganei joined Team Hokage because they are short of one member due to Fūko's inability to fight and to protect Yanagi, but Recca, Domon, and Tokiya still disapproves of Kaoru's proposal but allowed him to fight with Shiru. Koganei proves that he can fight very well and decided to fight again with Mokuren Nagai but is tricked and then trapped inside him and absorb his energy. Later, Kaoru is freed from Mokuren by Tokiya by defeating. On the orund between Hokage and Uruha Ma, Koganei Fights against Tsukishiro who wields two madōgous, Oboro which makes him invisible and Kaigetsu. Before the finals, a mysterious old man, which will be revealed as Kokū, in forms him about Kogan Ankis Sixth form, Mu but cannot tell how to do it because he "forgot" how to. Later that night Koganei persuades Saicho to come with him to check out the stage to be used but ends up with Saicho being severely wounded by Joker. On the finals, Kaoru fights Joker to avenge Saicho. While fighting, Koganei experiences minor changes with Kougan Anki and thought that this was failed forms but later learns that Kougan Anko can create many other forms and because he uses shortcuts when changing Kougan Anki, he misses the true path on forming Mu so he formed Kougan Anki using the long way around starting with Kiba, then Ryu, then Kyoku, then Tokiya and finally An. This leads to disassembling Kogan Anki making it "formless". Kogan then wraps the crystal ball holding Kogan Anki together around Joker and then reforming it making all the pieces pierce through Joker defeating him. In the anime, it is the same as in the manga with Koganei joined Team Hokage but this time both Domon and Fuko are missing due to both being fall into the trap and Recca disapproves him until Yanagi convinces him to join. He first defeated Shiru then being trapped by Mokuren as a human tree and using his energy to use all of Mokuren's powers only to be rescued by Tokiya during his match against Mokuren until he defeats him. He later watches the battle between Recca and Tokiya against Neon and Miki. He finally came to an understanding about Neon's story about Kurei and his tragic incident happened to Kurenai. Koganei later fights against Tsukishiro but both ends up in a draw due to his injuries and blood loss. After recovering, he and Saicho teamed up with Recca to defeat Magensha which happens to be the chief registration in disguise. However in his battle against Joker instead Koganei defeats him, Joker withdraws the match to make the battle fair between both Recca and Kurei but also not to reveal the Kogan Anki's sixth form.
Sealed Lands Arc
In SODOM, Koganei's first real opponent was Gaou at the Biodome, who was still seeking revenge against Domon. However, Koganei managed to defeat Gaou. Later, he faced off against Z to get the last data disc, which he succeeded in doing. Inside Hell or Heaven, Koganei ran into Joker, who was seeking a rematch. However, the two end up pairing up against Kirito and her pet Shiguma. They both defeat Kirito, but Joker sacrifices himself to defeat Kadotsu, who had survived Kurei's attack. Koganei saves Kagerō from Kōran Mori's minions, but is later overpowered as the main body comes out of the cocoon. At the end of the series he goes to live in the past with Kurei.
Koganei is amazingly athletic, able to outmaneuver a genetically altered Shiju who has lion cells in his body. Kaoru's greatest ability is his quickness and agility.
Kōgan Anki (鋼金暗器 Golden Blade): Kougan Anki is a "puzzle madōgu". It is a bladed weapon that can change into six different forms, the last one being a hidden form. Its primary stone has the symbol gold/metal (金, kin/kane) written on it.
Koganei is very good at solving puzzles, and can transform Kougan Anki in 0.6 seconds, while it usually takes a skilled user 10 seconds to transform.
- He is known as Lorkhan in the Filipino version of the anime.
- It's implied during Koganei's fight with Joker, that Kōgon Anki might have even more forms.
- In the manga, the Kōgan Anki was called a "magic golden staff". This is a reference to the chinese novel, Journey to the West. In the novel, one of the main characters, Sun Wukong, has a weapon that can change it's shape at will.
- In the English Dub of the anime during the Kurei Mansion arc, his voice as a kid has a high pitch tone until in the Ura Butou Satsujin arc, his voice changed into a teenage-like deeper voice. However, his voice is still Brett Bauer.