Ryoko was the first that Tenchi ran into.She had a hangover and claimed to be chased by a space pirate,and in the end she ends up being the space pirate,and she is being chased by the galexy police.
First class detective Mehoshi of the galexy police was chasing Ryoko when her ship crashed on earth.
Mehoshi sent a distress signle out for help,and it was picked up by the first princess of Jeri,who not only knows Ryoko,but had a battle long ago when they were children.
Sesami is Aieka's younger sister,who comes to earth to bring her back to Jeri.
Ryo-oki is Ryoko's space ship who is 1/3 rabbit,1/3 cat,and 1/3 space ship.Ryoko wants Tenchi to herself bad enough,that she tricks everyone into thinking that Ryo-oki is hers and Tenchi's child.