She, her sisters and their clan hail from an unknown province and for some time have kept a nomadic lifestyle, never settling down in a territory for too long.
One day they fought against the Asuka Clan. They were defeated but despite their surrender one of the Asuka ninja, Goh, killed Tateha against orders anyways. Since then Ageha and Usuba have sworn revenge against him.
Way of the Ninja
Attracted by the fires of war, the Mosu Clan came to Utakata not only to benefit from mercenary work but also to hunt down their sister's murderer.
Goh encounters them after finishing a mission. To their initial surprise Goh appears confused by their accusations and identities, but the sisters attack him anyways; they are defeated but Goh let's them go instead of killing them, the sisters are enraged by his mercy but choose to leave. From this point onwards they are fought regularly during missions, sometimes carrying Soul Fragments, unaware of the fragments nature.
Near the end of the game the sisters try to trick Goh by having Ageha disguise herself as Kinu. They prepare their ambush in Utakata Castle but encounter the real Kinu before executing their plan, shortly after comes Goh, now turned into a bear; in a panic Ageha tries to persuade Goh that she is the real Kinu but again this falls apart when Kinu reveals her prosthetic arm, confirming her identity. Unbeknown by everyone Uzumushi was planning an ambush of his own against Kinu for the death of Hebitonbo, and now completely confused by the presence of two Kinus he drops his mace against one, killing Ageha instead. The four remaining fight before Usuba retaliates against Uzumushi, chasing after he tries fleeing.
Usuba's fate is decided by the player. While she can be killed, her survival is considered canonical. If she lives she will send a letter to Goh before the final battle. In it she claims her quest for revenge has only left her more bitter than before and made her lose Ageha as well, so she's will return to her homeland to bury her sister and forget about her revenge, however the Mosu still consider themselves enemies of the Asuka.
Tales of the Ninja
Usuba returns as one of the three Ninja Masters in Tales of the Ninja. She appears as a boss in some missions.
One day many Mosu ninja are afflicted by a mysterious poison. Lacking any herbal knowledge to save them Usuba lets go of her pride and asks for Kinu's aid in private. Kinu accepts, delivers the antidote herb and complies with Usuba's request for her secrecy, to which the Mosu leader promises to help her back if she ever needs it.
Later Usuba and her clan are contracted to kidnap Princess Azami, thus stopping her marriage to Ichijo and the alliance of Tasogare, but are foiled by the Asuka. Shortly after they are sent to assassinate Ichijo before the wedding, but again they fail due to the Asuka's protection.
Revenge of Zen
Usuba and her clan return to Utakata once again as the political tensions worsen; she no longer holds a grudge against Goh or the Asuka but still considers them enemies. She is one of the many characters interested in collecting the Tenma Mirrors, if only for monetary reasons.
She manages to steal the Mara Mirror from a corrupt merchant before Zen does. Zen chases her to Rokudo Valley and both fight, but Uzumushi seizes the opportunity to steal the mirror when both are distracted. Later she is the first to find the Yaksha Mirror in Zengen Town, as is soon challenged by Zen for the mirror; Usuba loses and escapes but Nagi steals the mirror first anyways.
In one of the final story missions either her or Uzumushi will kidnap Zaji and demand the Tenma Mirrors in Zen's posession as ransom. The player may or may not rescue him:
- If Zen goes then he will find Usuba in Dandara Pass, ignore her demands for the mirrors and fight her instead, defeating her and rescuing Zaji who reveals that he let himself be caught to test Zen's morality (to Zen's mild irritation).
- If Zen ignores the ransom letter then a later cutscene reveals that Kaede defeated Usuba and rescued Zaji by herself.
As the master of the Mosu ninja, she is expert in their talents. In combat she moves fast, throwing kunai with deadly accuaracy and employing Mosu-style taijutsu when cornered.
What truly separates Usuba from the rest of her clan is the peculiar ability to create shadow clones. This clones move and attack the same way as her. The only other clan member with this skill is Ageha.
It's presumed she also has the same talent of disguise as Ageha, but this is not shown in any of the games.
She uses the same combat pattern as the rest of the Mosu: She prefers to keep distance and throw kunai at the player, moving constantly to avoid getting cornered; if cornered she will attempt to dodge, jump out of the way, grapple or attack with a strong melee combo. She is very fast and agile but cannot take much damage.
Unlike other Mosu she will create clones of herself if given the chance, these clones move the same as her and have the same attack power but can be killed with a single hit.
It's suggested to corner her or target her specifically to stop her kunai attacks and clone spell. If she creates too many clones try to make space and take them out one by one with caltrops or shuriken.
She's an ill-tempered woman with a confrontational personality. This affects her relations to her clan, as some letters have the Mosu vent and complain about Usuba's treatment of them.
She is violent and vindictive, quick to resort to aggression to get what she wants and more than willing to use trickery to obtain it. When an amnesiac Goh expressed his honest inability to remember his past, including the murder of Tateha, Usuba and her sister declared it of little importance as long as they can kill him. She also tries to trick him once with the guise of Kinu but fails. In Revenge of Zen she tries to use Zaji as ransom to get the Tenma Mirrors but Zen defeats and forces her to escape instead.
All things considered, she's shown to have a caring side towards her sister Ageha, and her death and Tateha's caused Usuba much grief. Also during a mission in Tales of the Ninja she asks for Kinu's help, despite her condition as an enemy ninja, to cure her poisoned troops and is genuinely grateful for the kunoichi's aid.
- Her name translates to "Thin Feather", following the bird naming trend of her sister and their clan.
- Out of all previous characters appearing in Revenge of Zen, she is one of the characters who went through the most redesigns phases.
- A cutscene in the first game shows that she and her sister have an interest in Kinu's body. Given their strange personalities this could be either attraction or admiration.
- She and her sisters share the same voice actress.
- She is playable as a skin model in Way of the Ninja and Revenge of Zen (playing as Kaede).