Just so everyone knows, their names are Emma Torikai (left) and Chizuru Mori (right), they are the protagonists of a series called Police and Lady that the author posts on their twitter and fanbox about Emma, a former prostitute meeting and falling in love with Chizuru, a police woman; after she saves her from a client. English translations are fanbox exclusive
^If I'm remembering correctly they're canon, and she's a masochist with a high pain tolerance. So they should be okay for her at least, but yeah nothing I'd ever want because ouch haha
^^ It's called Corset Piercing and to my (second-hand) knowledge "only" as painful as getting tattooed. The tricky part is the aftercare to prevent infection and irritation of the skin.