Katou Hideyoshi was a senior at Suzuran in Hana's first year and the leader of the Hideyoshi Faction. Nicknamed Mad Dog because of his proud and brash nature. He also seems to have some luck with the ladies - a fact that the other seniors are not very happy about.
Initially seen as the likely winner of the first year war, Hideyoshi lost to Zetton in the final round, and although the other finalists were able to find it in themselves to hang out together, Hideyoshi was hesitant due to the bitter defeat. However, as time elapsed he and Masa became more involved in the events concerning their year, and his involvement in many of the events playing a large part in the successful outcomes.
Hideyoshi also caused the spark that started the war between Suzuran and Housen when he took revenge for his best friend and right hand man Masa, who was attacked by Housen students. Because most of Suzuran's leaders were taken out separately over the duration of this war, Hideyoshi briefly assumed command of Suzuran's forces. This culminated in the final one-on-one match between him and Housen's King Joe.
Although a fearsome fighter, Hideyoshi has a tendency to challenge opponents stronger than him, because the challenge causes him to "burn up." Because of this, Hideyoshi has had a history of defeats ever since. Among the numerous opponents he's challenged (and lost to) include: Hiromi Kirishima, Zetton, and King Joe. However ,it is suggested that he was afraid to face Hanaki Guriko after he defeated Zetton.
Although seen as uncaring and cold for a majority of his time at Suzuran, his closeness with Masa to the point of leaving to Tokyo with him after graduation and becoming more involved with his friends to the point of hanging out with them showed he was just as human as the others. On the graduation day, he thanked Zetton and his other friends for the years he had at Suzuran, stating he was glad he could have met them when he did.
Left for Tokyo with Masa upon their graduation from Suzuran.