|“||Uhm, I... might not seem very flashy but...||”|
|— Karen Shinomiya, Online Character Profile|
Though she might give off the aura of someone who's confident in themselves, Karen is actually a shy and reserved girl. The reason she dresses in a flashy way is that she thinks if she dresses in such a way she’ll become less shy, which evidently hasn't worked so far. She also has low self-esteem, always referring to herself as simple and having nothing that stands out.
The reason she became an idol is similar to Yukiho Hagiwara in that she wants to change herself, but Karen also wants to become a role model for girls that have similar problems; to be proof that those who have low self-esteem might change themselves for the better. In short, she's a cowardly lion type (which she actually plays as a role she had in the event “Idol School Culture Festival”).