Kiku’s Secret Revealed!

Kiku and Raizo reveal themselves to the prisoners. Raizo is stated to be Fukurokuju’s biggest rival as a ninja. Kiku puts on a mask, causing the prisoners to recognize her as Kikunojo (his epithet is the “Lingering Snow”), a man, to Luffy and Chopper’s shock. Although he is male, Kikunojo says he is a “woman at heart” and so tends to act effeminately.

In truth, there were many things hinting at it: The clearest sign of Kikunojo’s gender is him referring to himself with sessha (拙者 or せっしゃ?), an archaic form of “I” used by male samurai. Kiku is wearing a Hannya mask. This is the important part about this character.
The Hannya mask is a mask used in the Noh theatre to represent the soul of a female turning into a demon due to obsession and jelousy, being Lady Rokujo one of the most famous representation of said characters. The Noh theatre was represented only by male actors in the past, with some of them playing only female roles because of their femenine features (some cases the actors only wear a mask to show the public that they are females). So Kikunojo is just like Izo from the Whitebeard Pirates. They both are men but they look and act like women. Probably Zoro had already figured it out!

O-kiku's role in Wano Arc

O-kiku's been in the town for about a month. Meaning that she could have been in another district of Wano her entire life and that there is no indication for a connection to any outside force. Her making notes of the Beast Pirates is pretty understandable even in that case, because many people suffered from the takeover of Kaido. She could be one of them, wanting revenge. The only real connection we have is that of Kikuhime, the character from the One Piece x Kyoto event. I guess she might be royalty that has a close connection to the Kozuki Clan. Maybe similar to Rebecca who was hated for her ancestry alone.

O-Kiku is a tea house poster girl who lives in the region of Kuri in Wano Country. It's later revealed that she is a female samurai. Kiku is a young woman with long dark hair that falls into her back. She wears sandals and a kimono with chrysanthemum floral patterns. She is a very tall person, easily towering over Luffy, Zoro, and Tsuru. She can be helpful as she helped prepare the medicine for Tama's illness. She is also courageous as when Tama was abducted by the Beasts Pirates, she was prepared to battle their forces to rescue her. She refers to herself with "sessha" (せっしゃ?), an archaic form of "I" used by male samurai. Kiku was working in the tea house when Urashima, a sumo wrestler from the capital, tried courting her to become his wife. She brushed him off and told him to place an order or leave, but Urashima simply continued bragging about his status. The situation was interrupted when Tsuru arrived with Monkey D. Luffy, Roronoa Zoro, and the ill Tama. Tsuru told Kiku to boil medicinal herbs for Tama, which she rushed to do. As Tsuru healed Tama, Kiku bandaged Zoro's wounds. Kiku then sat next to Tama while she was sleeping. She was alarmed when the gifter Batman attacked Tsuru. Another gifter Gazelleman abducted Tama during the confusion. After grabbing a sword and jumping on Komachiyo, Kiku then pursued Gazelleman along with Luffy and Zoro and head for the Bakura District.