A young prostitute in a brothel the Ittou-Ryu likes to use, and close with Magatsu Taito.
O-Ren is a prostitute shown lounging with Magatsu Taito in her brothel. It is assumed she and Magatsu may like each other, as Magatsu has spent considerable time in her room but has never touched her sexually. O-Ren always looks forward to his company.
She is in the brothel to earn money for her mother's medicine for an unspecified illness, but intends to leave once her mother recovers or dies and she no longer has to earn money.
Just after Magatsu leaves her for the last time, Shira goes to her room as a customer and interrogates her. O-Ren never says anything, even under torture and rape, and Shira eventually stabs her to death.
O-Ren seemed like a well-adjusted and calm young woman. She really enjoyed Magatsu's visits and intended to try being in a real relationship with him someday.