His first encounter with Usagi was when he killed a group of Dogora students with ease out of self defense. Amazed with his skill with the sword, Usagi followed him home in hopes of Katsuichi becoming his teacher. Katsuichi would prove that he was the toughest there is when it came to teachers, which would eventually lead Usagi to winning a tournament and going onto serve Lord Mifune. it would seem that on one of Usagi’s visits under the service of Mifune, Katsuichi and Usagi got in a fight with some Dogora students wishing to exact revenge for their embarrassment at the tournament. in the fight Katsuichi was blinded in one eye and fall to his apparent death. It would later be revealed that his body swept down river and that he was saved by two boys. In return, he would train these boys. Some time later, Usagi would later encourage his son Jotaro to seek out Katsuichi for training when he was of age.
As Usagi would continue on his warrior’s pilgrimage, he encounters an expert samurai by the name of Nakamura Koji. The two Ronin became instant friends, through their sharing of their old memories. Usagi learns that Koji was once a master of several forms of swordsmanship, as well as the head teacher of a prominent school. Koji was even set to become the dark lord Hikiji’s teacher, but before he would have the honor of having the dark lord as a student, he was set to have a duel with an upstart samurai. Not only did Koji lose once to this upstart, but as much as three times. Beaten and embarrassed Koji took this as a wake up call to how arrogant and prideful he had become. He decided to close his school and take up a warrior’s pilgrimage in order to hone his skill and someday defeat the upstart samurai. However Koji had a hard time finding him, because of the fact that the samurai was a recluse and trained only a handful of students. Koji would then challenge Usagi to a duel, revealing that the upstart samurai who beat him was none other than Katsuichi. Usagi and Koji begin their duel, at first Usagi is able to hold his own, however Koji eventually overpowers him. When it seems Koji is about to kill Usagi, he instead asks the ronin to deliver Katsuichi a message. Koji asks Usagi that he challenges Katsuichi a year from then at Kitanoji temple for a final duel. A year almost passes and Katsuichi begins to make his journey to the temple, along with his current students Shunji and Jotaro. Along the way, they reach a village that has bandit trouble. Usagi and Koji meet them there and they all join together to defeat the bandits. In the mean time, Usagi has been able to pick up a major flaw in Koji’s technique, which would easily give Katsuichi the upper hand. Katsuichi refuses this information and states that he will face Koji on equal grounds. The next day Koji and Katsuichi take their places and draw their swords. Usagi anticipates the outcome of both men, being so evenly matched, killing each other. The two sword masters charge and strike. A couple seconds pass after the two’s initial charge at one another. Then blood drips from Koji’s mouth and shortly after he collapses dead. Katsuichi then states that Koji was a true samurai and that there will be none better.
Katsuichi’s mysterious past has just recently been revealed, he and his friend Isao were both students at a sword school. Katsuichi and the daughter of a rival school, Kinuko, are deeply in love. However, the best student of Kinuko’s school, Toji, despises Katsuichi. Toji is filled with ambition and greed to become the master of Kinuko’s father’s school. Toji sees Katsuichi as an obstacle preventing him from gaining what he believes should be his. Katsuichi and Isao talk about Katsuichi’s relationship with Kinuko. the two get into an argument. Katsuichi is supposed to take over his school, when their teacher passes away. However, Isao is frustrated that Katsuichi has no plan to take over the school. Katsuichi explains to Isao that he has come to question some of their teacher’s philosophies. and that he is not worthy of taking over the school, rather Isao is better suited to do so. Isao understands and the two part ways. Katsuichi then asks Kinuko to accompany him on his warrior’s journey, however Toji ambushes Kinuko and tells her that her father has set the two up to marry. Kinuko tries to escape and scratches Toji on the face. In his rage, Toji kills Kinuko. Realizing what he’s done, he begins to blame Katsuichi for ruining his plans, Toji confronts Katsuichi, the two charge at each other and Katsuichi kills Toji in one stroke.
It should be noted that while Katsuichi will never admit it in front of his other students, he sees Usagi as his greatest student.