Kin

Kin, better known as Kohana, is a young woman who worked alongside Akesato in Shimabara.

Story
Kohana is introduced early on in Volume Two of the series as a prostitute in Shimabara. A few years before the current storyline, and before selling herself as a prostitute, Kohana was married to a young man named Shonosuke under the false pretense of being the daughter of a monk. When Shonosuke’s mother found out, she had the marriage dissolved, even though the couple was deeply in love and even had a young daughter together. Distraught but determined to make it on her own, Kohana becomes a prostitute in Shimabara, sending money back to her father and daughter, both of whom she seldom gets to visit.

With her husband ripped from her arms, and her future uncertain as a prostitute, Kohana is visibly miserable and upset waiting for customers in Shimabara, which causes Okita Souji to notice her. He later decides to visit Kohana, and surprises her by saying that he has no intention of sleeping with her and only wishes to sleep. Kohana is thrilled to be paid and not have to fulfill her "duties". Soji soon becomes Kohana’s patron and only asks that she keep his secret. Once a month, Soji would also act as a messenger, bringing information to and from Kohana's daughter.

Kohana soon becomes Souji's "favorite prostitute" in the area and the only woman he visits, something the other men don't understand. When Sei finds out that Souji likes to frequent a woman in Shimabara, she slaps him, and hates herself for thinking that Souji would be any different from the other men (she, of course, has no idea that he doesn't use her for sex).

It's not until later that night, after Sei is forced by the other men to visit Shimabara so he can "become a man", that Akesato tells her what is really going on between Kohana and Soji.

Later in the series, we see that Kohana has fallen in love with Soji, and has been waiting and hoping that one day he would return her feelings. When troop regulations change, allowing captains to have private quarters, Soji is able to redeem Kohana and set her and her daughter up in a private residence. Kohana is thrilled at his offer, thinking that perhaps he has finally learned to love her too, but eventually she realizes that Soji will never love her and declines his offer.