Sei is often described as "feeble". He is very pale with black hair and eyes. He wears a studded black fedora with a Morphine pin on the side. Sei wears an open shouldered, long sleeved white shirt that has black straps over his shoulders. He has matching jeans and gloves that have skeletal designs, with wears a half skirt that is connected to the right side hem of the pants connected by black suspenders that hang on either side of his body. Two studded collars adorn both his neck and wrists. He also wears a pair of white boots with black studs.