One of the main protagonists and a veteran superhero past his prime whose total disregard for private property when fighting against crime earned him the nickname "Crusher for Justice". Originally, he was the least popular among the heroes of Sternbild City and his company (a fictional publication known as TopMag) had been taken over. He was then forced by his new employers to become Barnaby's partner. His wife died from a disease five years prior to the series, and his daughter Kaede lives with his mother. Like most people of the city, Kaede is unaware of his secret identity, and she resents her father for always being tied up with "work" and unable to see her. He possesses the power to increase his physical abilities hundredfold for five minutes (known as the "Hundred Power"), after which he cannot use it again for one hour. Later on in the series his ability starts to change, becoming more potent but burning out faster. Tiger's old employer, now working as a cab driver, finds out about Tiger's power boost and informs him that it is actually a precursor to his powers fading away for good. The Hundred Power's time limit now grows shorter with each activation, currently being around three minutes, 45 seconds. Kotetsu keeps a journal to track his decreasing power, each entry showing a decrease of two to five seconds per use.

His new suit includes advertisements for the Japanese S.H. Figuarts toy line and Japanese media company SoftBank. Tiger also possesses a motorcycle, which is able to combine with Barnaby's own bike as a sidecar. Having been inspired by a hero named Mr. Legend, who helped him to accept his powers, Kotetsu has traditional ideals of justice, always relying on his instincts, putting lives over ratings, and prioritizing hero work over publicity stunts. After helping Barnaby defeat Jake Martinez and finally earning his partner's trust, Kotetsu has become far more popular and has gained much more respect from the public, his employers, and his fellow heroes. In the first Drama CD for the series, it was revealed that Kotetsu and Antonio "Rock Bison" Lopez were punks in their high school days, and it was their class representative (who later became Kotetsu's wife) who came up with the name "Wild Tiger".