Kotetsu Hagane

is a chūnin-level shinobi from Konohagakure.

Appearance
Kotetsu has long, spiky black hair and dark eyes, he also wears a bandage over his nose and has a light-coloured patch on his chin. He wears the standard attire of a Konoha shinobi complete with forehead protector and flak jacket. When deployed on missions, he usually carries a pair of Kunai Blades strapped to his back.

Personality
Kotetsu is almost always seen alongside Izumo, and is characterized as being the irresponsible and less conscientious one of the duo. He was seen, for instance, at the end of Shippūden Episode 81, shirking his duties and eating a large jar of syrup by himself in the Jōnin lounge. Similarly, Izumo admonished Kotetsu's lack of pride in his work when the latter complained that they were simply Tsunade's errand-boys or "gophers". He has also been depicted as being the more carefree and more volatile of the two. He is also described as being curious by nature.

Abilities
He is proficient with genjutsu as was seen during the Chūnin Exams in Part I, when he uses Demonic Illusion: False Surroundings Technique as an unofficial preliminary test of the new genin.

He is also proficient with weapons as seen in Part II, during his fight with Kakuzu, Kotetsu summons a large shell-like weapon from a scroll he was carrying. Since he was quickly captured by Kakuzu after this in the manga, it is unclear how skilled he is with it. However in the anime, it was shown to be able to perform aerial assaults. He also carried two large Kunai Blades with him which he wields with great proficiency.

Chūnin Exam Arc
Izumo and Kotetsu first appeared disguised as Genin, trying to convince those planning to take part in the Chūnin Exams not to bother. Team 7 recognized that they had cast a genjutsu on the area, prompting them to give up in light of the group's skill. They then acted as examiners in the first test. When Tsunade became Hokage, Izumo and Kotetsu started doubling as her assistants and as guards to the front gates of Konoha. The anime indicates that they are easily ignored or duped by those using the Transformation Technique while on the job.

Sasuke Retrieval Arc
During Tsunade's transition into office he and Izumo Kamizuki became the assistants of Tsunade. They were the ones that found Sakura in the morning after Sasuke left Konohagakure and later informed Tsunade about the incident.

Pre-Shippūden Filler Arcs
Along with Izumo, he makes a few cameos in filler arcs. The first was the two of them carrying the chair Tsunade had kicked out of her office back to where it belongs. Izumo has a huge bleeding lump on his head as if he was the unfortunate recipient of the chair. The second is them guarding the entrance to Konohagakure, when the fake Naruto, Kiba, and Hinata enter the village. They express shock as the real Naruto and Kiba appear, as they had passed just minutes ago.

Kazekage Rescue Arc
Kotetsu is seen with Izumo relaxing as Teams Guy and Kakashi are returning from saving Gaara from the Akatsuki.

Twelve Guardian Ninja Arc
Kotetsu is among the ninjas defending Konohagakure from Furido and his team of ninja.

Hidan and Kakuzu Arc
Izumo and Kotetsu were assigned to a Nijū Shōtai team with Asuma Sarutobi and Shikamaru Nara, their mission being to find members of Akatsuki. They successfully managed to do just that. The team tracked an Akatsuki duo to a bounty station, where Izumo and Kotetsu stabbed Hidan during a sneak attack. When Hidan survived, they pulled back and were forced to watch Asuma fall prey to Hidan's jutsu, unable to help him. They instead engaged Hidan's partner, Kakuzu, but were easily captured and had to be rescued by Raidō Namiashi and Aoba Yamashiro.

Invasion of Pain Arc
In the anime, Kotetsu is inserted as a member of the Konoha Barrier Team and is seen playing cards with other members when he hears about an intruder breaching the barrier.

Later, after Pain's invasion, he and Izumo were seen with Genma helping to rebuild the village. Kotetsu said that the Akatsuki had taken away everything that their forefathers had left for them.

Konoha History Arc
With himself as captain, he sent out on a mission to retrieve Condor from Training Ground Zero with Naruto Uzumaki, Rock Lee, and Shino Aburame. During his battles with Condor, he experiences near death multiple times. Moments before his eminent death, his partner Izumo arrived to save him using their combination of Izumo’s Water Release: Syrup Capture Field and his own Conch Shell Mace to defeat Condor.

Shinobi World War Arc
After the defeat of the Gold and Silver Brothers, Izumo and Kotetsu launch a surprise assault on Kakuzu slashing him with their Kunai Blades and immobilizes him by wrapping the chain attached to the blades around him. Kotetsu then says they came to repay him from their last encounter. They then ask Ino, Chōji, and Shikamaru to help them seal him. Shikaku contacts the two and informs them, that he and Izumo, along with Darui would deal with Kakuzu, while Team 10 would fight Asuma.

He and Izumo are later seen standing over a defeated Kakuzu who was being restrained under Chōji's colossal fist.

Trivia

 * During the third Naruto OVA that came as a bonus with Naruto: Ultimate Ninja 3, Kotetsu engaged in a fight with Gaara, resulting in a humiliating defeat and a few broken bones after Gaara used Sand Waterfall Funeral on a weaker scale.
 * translates to steel and translates to iron.  is also similar to, which can also be translated as steel.
 * In the anime it was shown that Kotetsu likes to eat pure syrup.