Kotetsu Hagane

is a Tokubetsu Jonin from Konohagakure.

Part I
During the Chunin Exam's first test, he was sent to test the Genin by casting a Genjutsu, which made the Genin see the second floor as the third. Later on the third test, Kotetsu and his friend Izumo Kamizuki watched over the Chunin exam, giving feedback on the Genin's qualities.

Part II
After Tsunade became Hokage, Izumo and Kotetsu served as her assistants, Kotetsu stated Tsunade as "a real slavedriver", a trait which Tsunade really has. After the timeskip, Kotetsu, Izumo, Shikamaru and Asuma served as a team to track down one of the Akatsuki's pair, Hidan and Kakuzu, but resulted in failure along with the death of Asuma.

Abilities
The abilities Kotetsu has show us so far through out the anime and manga is that he is skilled in Genjutsu, having made the 3rd floor of the Academy appear like it was the second. In the Manga he has been seen summoning a large mace conch shell against Akatsuki members Kakazu and Hidan. Its destructive abilities are never shown due to Kakazu countering his attack