Sendai Girls' Pro Wrestling
Shirai made her professional wrestling debut on March 4, 2007, alongside her younger sister, with the two adopting the ring names Mio and Io Shirai, respectively ("Shirai" being Japanese for "Purple Thunder"). While both of the sisters initially kept much of their private lives, including their real names, a secret, Io's real name was released by Japanese authorities in May 2012 as . Mio, on the other hand, has managed to keep her real name a secret. In their debut match, the Shirai sisters teamed with Toshie Uematsu to face the trio of Erika Ura, Nozomi Takesako and Yuri Urai. Starting their careers as freelancers, the Shirai sisters represented Team Makehen, a stable made up of wrestlers trained by Tomohiko Hashimoto, in several independent promotions during their first year in the business, including Ibuki, Pro Wrestling Wave, JWP Joshi Puroresu, and Sendai Girls' Pro Wrestling.