Saitou is a former leader of the third group of the Shinsengumi. One of the groups that they were fighting for was the Ishishishi. When the Tokugawa government was overthrown, Saitou joined the Mieji governments secret police. For one of his missions, he was sent out to test Kenshin's ability and see if he was able to defeat Shishio Makoto. However, when they start fighting, they were unwilling to stop because they had never finished the fight they had before the new era started. Kenshin returns to his evil self, and is oblivious to everyone around him. But then a government official comes into the dojo, they stop and Kenshin punches himself. This punch brings him back to his normal "de gozaru yo" self. Saitou lives his life by one quote "Aku, Soku, Zan."

Saitou uses a Japanese Katana (breaks many of them during fights) uses the technique Gatotsu. This technique has the capability of cutting through any object. The Gatotsu also involves several stances, ranging from three to zero (I believe). The zero stance is the most powerful, being the fastest stance in the technique. Saitou would thrust himself forward with incredible speed, having his sword aiming towards his opponent.