A clone of a legendary itinerant monk, Ikkyuu is one of the I-Jin. The I-Jin were a series of clones of legendary historical figures created by the Dokusensha for unknown purposes. What is known is that the I-Jin (literally "Great People") escaped the will of their master, following the lead of the charismatic Ikkyuu.
Ikkyuu, unfortunately, does not share all his traits with his genetic ancestor. He is insane, viewing the world as it exists in the twentieth century as hopelessly corrupt and ignorant. When he learns of the Suicide Symphony, a musical score created by Beethoven that caused all who heard it to commit suicide, he set out on a quest to recover the symphony and use it to cleanse the world of humanity. To this end, he has forged the other I-Jin into a powerful organization of unstoppable assassins that will stop at nothing to fulfill his vision.
Ikkyuu appears very calm, and talks in a very clear, zen-like manner. He discusses beauty and destruction with the same outward detachment. In reality, he is a cruel and petty man. He will not heistate to kill those he feels has slighted him or those he no longer finds useful. He is a womanizer, and even planned to kill the clone of Mata Hari when he felt she had drifted even slightly away from him, replacing her with a more obedient version of the same woman.
Like all the I-Jin, Ikkyuu was granted superhuman powers by the process of cloning. Whether this was a side-effect of the process or a deliberate act on the part of their creators is unknown. Ikkyuu is a fair-to-middling martial artist, capable of using his skull-adorned staff as a melee and ranged weapon to lethal effect; the staff can also produce flames. Finally, Ikkyuu can generate illusions using the medium of traditional Japanese watercolor scrolls. These illusions have no substance, but serve as elegant distractions in a crisis.
Ikkyuu's true power resides in the force of his charisma and personality. He is very clever, and able to unite a loose collection of eccentrics and egomaniacs into a unified force. The force of his charisma is almost hypnotic - he is capable of so deeply enforcing his will on others that they could not bear to betray him, even for their closest friends.