"Twilight" Suzuka is one of the most feared freelance assasins in Outlaw Star. Her nickname comes from her trademark of only killing her targets as night falls; if delayed from taking care of business, she would actually leave and come back the next night to kill her target at the
Spoilers of various sorts ahead, though nothing major.
A competitor of Fred Lou hired Suzuka to kill Fred, because Fred's weapons dealing business was threatening to cut into his own. On the same night Suzuka came to kill him, Gene Starwind came to Fred to ask for a loan, and managed (barely) to save Fred's ass (and his own) when Suzuka came to kill Fred. She vowed to return the next night to kill him, and Fred begged Gene to protect him (as his own bodyguards had lasted about 2 seconds against Suzuka). Gene was most reluctant, but decided to do it after Fred promised to make him another loan. The second night ended with a one on one fight between Suzuka and Gene, and ended in a bit of fan service when Gene pulled on the large bow holding Suzuka's kimono together, leaving her a bit... revealed. In return for Gene returning the bow, Suzuka agreed that before killing Fred, she would have to kill Gene. This would allow Gene to protect Fred by protecting himself, which made his job a lot easier.
Suzuka's primary weapon is a bokuto through which she channels magic. Since the bokuto is made of wood, it is not picked up by weapons scanners, which tend to assume any weapon will be made of metal or artificial materials. She can do things that nobody has the right to do with a piece of wood, such as cutting a semi truck in half, lengthwise. Along with Aisha, Suzuka is the primary fighter in the crew of the Outlaw Star.
Suzuka's personal history is never revealed, aside from the fact that Hitoriga, one of the Anten Seven, killed her entire family, and took her face as his own. Eventually, Suzuka joins the crew of the Outlaw Star (at first she claims she does so in order to kill Gene), and while always staying a bit formal with everyone, it is hinted at various times that she is in love with Gene. By the end of the series, her employer cancels the contract on Fred (of course, maybe her employer got cancelled once Fred found out who hired her), and so she has no reason to kill Fred or Gene. She ends up joining the crew full time as they search for the next big job.