Okiku is a tea house poster girl who lives in the region of Kuri in Wano Country. She is also a samurai.
Her real name is Kikunojo and she's is a samurai from Wano Country and a retainer for the Kozuki Family, serving as one of Kozuki Oden's Nine Red Scabbards.
It's later revealed that Okiku is male but identifies herself as a "woman at heart", and thus presents herself effeminately.