Yoshimi is Kaoru's gravure idol elder sister that is about Minamoto's age. Given the prominent cleavage that both she and Akie have, it can be argued that the origins of Kaoru's lesbian lechery lie here. As pointed out by Akie, a gravure idol appears to be a sort of trainee-entertainer designation. Considering the 11-year difference in age, Yoshimi is probably not really affected that much by her parents' divorce and just has no clue how to help Kaoru. Like with Akie, she deals with this with her work and dating.

(Source: Wikipedia)