Kurogasa, otherwise known as Udou Jin-e, was a hitokiri during the Revolution, and there is evidence he continued killing people well after the end of the Revolution. He attacked high-ranking Imperialist officials of the Meiji government (leading some to believe he fought for the Tokugawa shogunate during the war, since he did state that he was a member of the Shinsengumi, though his thirst for blood led him to killing members of his own squad), killing anyone who stood in his way. He appears as a man dressed in a long scarf, straw hat, and long kimono, and has a unique ability to project his "swordsman's spirit" toward people, hypnotizing them with his eyes (known as the Shin no Ippo). It can also be used to strengthen himself. Kurogasa is obsessed with defeating the famous Hitokiri Battousai (Himura Kenshin) when he meets him during Kurogasa's attempted assassination of Mr. Tani, a government official. He leaves, stating that if Kenshin cannot fight him to his fullest potential, he doesn't want to fight him at all. Kurogasa ends up kidnapping Kamiya Kaoru the next day, in an effort to force Kenshin to once again become a hitokiri. Kenshin follows Kurogasa's trail to the forest, where the two duel once again.

Despite Kaoru's life being in danger, Kenshin still didn't fight with the intent to kill, and Kurogasa overwhelmed him. Not wanting to settle for Kenshin holding back Kurogasa paralyzes Kaoru so she cannot breathe using his Shin no Ippo, the two resume the battle. Kenshin eventually becomes angry enough to turn back into the Hitokiri Battosai, and completely overwhelms him, braking his arm. Kenshin raises his sword to kill him, as Kurogasa looks on gleefully, but Kaoru's pleading for him to stop releases Kenshin from his Battousai spell. Kenshin then frees Kaoru, while Kurogasa picks up his sword with his other hand, and stabs himself in the heart.

(Source: Wikipedia)