Kurogane is a ninja warrior directly under the service of PrincessTomoyo (a crossover character from Cardcaptor Sakura's Tomoyo Daidōji) of Shirasagi Castle. While he is undoubtedly the most powerful warrior in Nihon Country which is the the kingdom of Japan, he shows no mercy to any assassins who try to invade the castle, killing them on the spot, even though Tomoyo has asked him numerous times not to kill them. Short-tempered and a dear friend/servant to Tomoyo, the princess eventually decides that he needs to be sent to Dimension Witch Yūko Ichihara. Before she sends him off, Tomoyo curses him such that whenever he kills someone needlessly, he will grow weaker so that he discovers what true strength is.
Kurogane, upon his arrival in the shop of the Dimension Witch, is the least informed as to who she is, but the most certain about what his wish is: he wants to return to his own world. Like his soon-to-be travelling companions, he must pay with what he values most to gain the ability to traverse dimensions. For Kurogane, it was his sword Ginryuu. He reluctantly agrees to give up the sword, but asserts that he will come back for it someday.
Kurogane is serious and extremely perceptive, being able to quickly discern Syaoran's fighting ability (along with Syaoran's blind right eye) as well as Fai's true nature and fighting capabilities. While he seems rather irreverent, he is also very loyal, especially to Tomoyo. He is likely the most experienced fighter in the group and wiser than he appears. He becomes Syaoran's sword fighting teacher, presenting the boy with the same philosophy he believes in: a sword is used to cut only when needed and not used to cut anything if it is not necessary. While serious, Kurogane is very easily irked by others, especially by Mokona Modoki and Fai, who keeps calling him ridiculously cute nicknames such as "Kuro-puu", "Kuro-wan-wan" or "Kuro-rin". However abrasive and ruthless Kurogane may seem, he has a compassionate nature and a desire to protect. An example of this would be how Kurogane continually questions Fai on his actions and character, and lets the wizard know that he should stop hanging onto his past and embrace the future with his new companions. Or, Kurogane's own statement that "If someone wants to take away the ones I want to protect, I'll kill them too."
He had told Syaoran in their first world, the Hanshin Republic, that the quest has nothing at all to do with him. In the next world they visit (Koryo Country) however, Kurogane offers his services to help raid the castle of an evil lord, and stays behind in battle to let Syaoran go on ahead. Eventually, he risks a loss in strength to avenge his comrades' "death" (they were of course still alive) by defeating their killer in battle. It is noted that after he finds out Fai and Syaoran are still alive, he lost his passion for the battle.
He obtained a new sword in Ōto called the Sōhi (Blue Ice) and taught Syaoran the skills of sword fighting and sensing attacks from the left. Thanks to Fai, Kurogane could summon his sword from his left hand in a similar way to Syaoran in case Mokona was not there to give him his sword. However, he sacrified this arm along with Sōhi to let Fai escape from Celes after hearing Tomoyo speak to him through telepathy, saying "If you wish with all your heart to keep him by your side, exchange for him that of equal magic." Kurogane shows much more inner compassion from his actions in the latest chapters, such as the aforementioned rescuing of Fai from Celes.