Name: Kasumi Fuu
Age: 15
Profession: Varies (usually a waitress)
Weapon(s): Tanto
Fighting style(s): N/A
Quote: "My mother and father...died when I was very little.","I'm starving..."
,"I'm looking for a Samurai who smells of Sunflowers." Appears in: All episodes
Final status: Alive

Fuu (風) is the leading lady of the show, a fifteen-year-old girl of samurai lineage, but brought up in poverty. After a not-so-successful stint as a teahouse waitress, she saves Mugen and Jin from execution and forces them to help her on a quest. She is searching for the Samurai who smells of Sunflowers, but never explains what a sunflower smells like or what the man looks like. Mugen and Jin are often reminded of their life-debt to her when they wish to fight each other, much to their chagrin. Without her father around to support them, Fuu and her mother led a difficult life until her mother died of illness.

She is a surprisingly big eater (in one episode she entered an eating contest and was one of the last two remaining and would have likely won had she not accidentally given the sign that she gave up by squishing a bug), has a bright and trusting personality, and is strongly prone to accidents and trouble although she is quite practical. She often puts on a front of being more worldly and experienced than she actually is so as not to appear completely ingenuous in front of her bodyguards. Fuu wears a deep pink kimono with a pattern of flowers and carries a matching tantō (which she never uses, but has brandished once or twice). Attached to the tanto are three netsuke: a skull (a Christian pendant from her father), a pair of dice (probably referencing her dice-rolling skills in "Hellhounds for Hire") and a dog. A flying squirrel by the name of "Mo-mo" (evidently short for "momonga," which means "flying squirrel" in Japanese) inhabits her clothing and frequently helps out when she's in trouble. Momo also means "Peach" in Japanese, and is a popular modern pet name in Japan.

A running gag throughout the show is Fuu becoming impossibly huge after overeating, reverting to ordinary form after her stomach has digested everything. This occurs in Episodes 6, 15 & 23.

While there might be implication that she might be in love with Mugen, truthfully Fuu could possess feelings for either Mugen or Jin. It is hinted in some episodes, most notably episode 20- first Sara talks about her possible feelings to one of Fuu's "bodyguards", and then she chooses to travel further with Mugen, sending Jin with Sara (although she admitted to Mugen that she thought Jin would've said no). Then, in episode 24, she cries by the river and mentions Mugen in conversation with Jin, but doesn't finish the sentence. Jin uses this later (episode 25) to decide who stays and fights Kariya Kagetoki, and who runs to rescue the girl, saying: "Take care of Fuu", showing his understanding of Fuu's feelings towards Mugen.

Her voice actress in the Japanese version is Ayako Kawasumi. She is voiced by Kari Wahlgren in the U.S dub.