Kotetsu is one of the fighting dogs owned by the Tachibana family, and the second that appears in the series. His special attack is the Tōken Gyorai. He faced Mr. Akiba's dog and Kaizan in informal training matches, and won them both. Later, Kotetsu faced Yamato in a fighting dog match, which was the first official match for both dogs. Kotetsu wounded Yamato with Tōken Gyorai, but Yamato won against Kotetsu by using Kaiten Jigoku. Kotetsu later took part in the Yamagata District tournament and fought against Sakahoko.