Ryoko Masaki
TV series
Sort of an outcast throughout her life, she has turned to a life of crime. An infamous space pirate, she is one of the most wanted by the Galaxy Police and chased by countless bounty hunters. Nowadays she hangs around Earth with the Masaki family, always has her eye on Tenchi (and everything else for that matter).
Note: Ryoko self-named herself Masaki, she is not at all related to the Masaki family.
Ryoko
Pretty Sammy Series
One of my favorite (and lagging) students, she has the tendency to pick fights and show-off to Tenchi. Matter of fact, she has the tendency to kidnap Tenchi too.