Osuzu

Daigorou's demure daughter; she is quite something to look at. Before she is forcibly procured by Ishimatsu, as an excuse to make up for Sousuke's insolence, she was the latter's tutor.

[Spoiler] She is put to work with in one of Rikiei's brothels, where she meets Fuu (who is also being forced into prostitution because of bad fortune) and they become friends. Both are emancipated after Rikiei's demise. [/Spoiler]

(Source: Wikipedia)