This is AUH's residenty super ninja. He's got the standard baggy pants and stupidly long scarf, so you can tell he's serious. However his nickname is the misty red death because of his nifty ability/curse. He was born with a horrid condition in which his blood cells constantly die and his body can't keep a constant supply of fresh blood. Instead of waiting to die, he implemented a system wired into his body that expells the dead blood as a red cloud from out of his body. This serves to get of rid of the dying blood from his body and an effective smoke to do all of his ninja-stuff.
This means also that he must constantly obtain fresh blood to survive, which is what his weapons do. They retain blood from the wounds he inflicts on opponents and filters the blood in that cartridge at the end of handle. He then can inject fresh blood into his system.
Hius rival in the story is Tamasuboro of the Silverheart sisters.