Minagi (巫薙) is a manga only character, that is a character that has only appeared in Hitoshi Okuda's No Need For Tenchi! and The All-New Tenchi Muyo! manga series. She can be considered the equivalent of Zero from the OVA series.
Minagi looks identical to Ryoko, except for two thin red marks, one on each cheek. She has almost identical abilities and strengths, but is defeated by Ryoko. She was created artificially by Yakage who stole a sample of Ryoko's DNA and spliced it with his own, making her essentially Ryoko's half sister. Minagi was born as part of Yakage's plan to create the "Ultimate Sword", that could surpass the Tenchi-ken; and make Minagi the owner of his sword. After Yakage's defeat by Minagi herself (as she lost her memory and fought her master in order to recover it), she becomes a bounty-hunter/space pirate like Ryoko was, however she only steals from greedy rich people. She occasionally visits Tenchi and the others, sometimes helping them during troubles.
Minagi is outgoing and truly polite, in contrast to Ryoko, who is somewhat rude and hostile. She eventually develops a special relationship with Washu, considering her mother (which she technically is).