Nao Oikawa

In Spring 2002, Oikawa began an association with the new KMP Million label, most of them under the direction of Goro Tameike. She said that Tameike showed her the way to go. Her first video with KMP and Tameike, Another Side of Nao Oikawa, involved anal sex and forced fellatio. One of her male partners is famed porn actor Taka Kato. About same time, she began to work with Soft On Demand and Moodyz which produced her most popular AV works. More than half of her AV work are produced in 2002.

In Spring 2003, Oikawa signed exclusive contract with KMP which continued until her retirement. Together with Ran Monbu, Saori Kamiya and Hitomi Hayasaka, she was part of the exclusive group of actresses that KMP used for promotion under the name "2003 Million Girls". Another Side of Nao Oikawa 2, was even more hardcore with lesbian strap-on sex, forced fellatio and vomiting, multiple partner fellatio and vibrator play. Once again Taka Kato takes part in the action. On a gentler note, Oikawa appeared with Kurumi Morishita in a June 2003 production by KMP entitled Forest in Nude. Directed by TOHJIRO, this lesbian genre video is a "soft, bittersweet story of two friends who remember the days of their youth and the sexual experiences they had".

At her peak, Oikawa was one of the most popular and well-known AV Idols in Japan. In 2003 she was #1 in the DMM list of the 100 top-ranked actresses by sales on their website. In 2004, even though she had retired in mid-year, she was still ranked #2, and even in 2005 she made the top 50 at #42. There have since been numerous re-issues and compilations of her earlier videos. Oikawa, along with fellow AV actress Mariko Kawana, actor Taka Kato, director Goro Tameike and Soft On Demand founder Ganari Takahashi, was among the 17 people interviewed for Misato Nakayama's study of professionals in the adult industry, 性職者の人々 あの世界の仕事師たち, published in January 2006 by Ohzora.