Is it me or does she remind you of Hinata from Naruto?
She's 15 btw, like Sailor Venus, Orihime and Pan from GT!
She is a female ninja who is soft spoken and not very confident fighting immortal samurai. She is in love with Shishimaru Tenoh and tries to save him from Ginnai Doma at the start of Black Lion and is killed by him.
She was voiced by Yuri Amano(Not the Wedding Peach Babe) who was also Momoko Ishiyama in All Purpose Cultural Cat Girl Nuku Nuku, Yukiko Shirane in Abashiri Family, Kate in Bondage Queen Kate, Nanbel in Burn Up, Kawai Kawai/Iczelion Silver in Iczelion, Mary in In The Beginning - The Bible Stories, Alcione in Magic Knight Rayearth, Holy cr-p she did Rain Mikamura in Mobile Fighter G Gundam!! Hot!! Gold Digger in New Cutey Honey OVA 8, Birdy and CeleCele in Sailor Moon, Kiyone Makibi in Tenchi Muyo, Makiko Nagi in Tenjho Tenge, Princess Elise and Naria in Escaflowne, some chick in some Violence Jack oav and Keiko Yukimura in Yu Yu Hakusho.
In the dub she's voiced by Jessica Looney who was Nurse and Young Boy in Variable Geo(Hot), Senior girl in Dazed and Confused, Perky Girl in One Tree Hill and Silver Iczelion in Iczer gal: Iczelion.
In the manga she was the grandkid of the guy who trained Shishimaru and they grew up like bro and sis. At age 15 the Chief Sandayu Momochi called her over and checked out her nude body (As Go Nagai likes naked chicks) and she's selected to be the concubine of the Daimyo where she can spy on him. After Shishmaru finds out, he wants to skip town with her and is gonna slag her grandpa but cant and gramps tells him to do it, which he does (head flys off). They book it but Goemon Ishikawa confronts them and takes Oyu hostage to get the edge in the fight against Shisshimaru. he gets her naked, ties her up and puts pit vipers on her as she hangs from a tree. So Shishimaru kung fu fights Goemon and Oyuu flips the snakes off but this ugly bast=rd Geni comes by and cuts the tree branch she was on off and catches her. So Shishimaru cuts down Goemon across da gut but leaves him with enough flesh left so he can live, but if he moves too much, his guts will spill out like that chick in Violence Jack with the psychic girl. After Shishimaru saves her from the ugly bast-rd, the cheif Momochi comes by and they have a duel. If Shishimaru wins, they get to go free. If not, they follow the Ninja Code. In the fight he somehow switches places with Oyu and Shishimaru slices her in half head to crotch. And then... She died... AHHHHHHHHHHHHH!! Shishimaru goes like Vegeta when Cell slagged Trunks but Chief beats him down saying if Shishimaru was better he wouldnt have fell for his substitution jutsu and if he wants to rule, get strong! After beatingg down Shishimaru, Shishimaru sez he's gonna be the very best and ice Momochi