She started her career in March 2007, working alongside her sister Io Shirai on the Japanese independent circuit for promotions such as Ice Ribbon, JWP Joshi Puroresu and Pro Wrestling Wave.

[4] In their debut match, the Shirai sisters teamed with Toshie Uematsu to face the trio of Erika Ura, Nozomi Takesako and Yuri Urai.

[25][26][27][28] On April 29, the Shirai sisters won their first championship by defeating Moeka Haruhi and Tomoka Nakagawa in a tournament final to become the first TLW (Totally Lethal Wrestling) World Young Women's Tag Team Champions.

[33] On November 25, the Shirais and Gami first defeated Bullfight Sora, Cherry and Kaoru in the semifinals and then Ayumi Kurihara, Kana and Shuu Shibutani in the finals to win the tournament.

[37] On June 19, 2010, the Shirai sisters formed the Triple Tails stable with fellow freelancer Kana, defeating Ayumi Kurihara, Hikaru Shida and Yoshiko Tamura in their first match together at a NEO Japan Ladies Pro Wrestling event.

[40] Triple Tails returned to its winning ways on August 29, by defeating Asami Kawasaki, Hikaru Shida and Nagisa Nozaki in a six-woman tag team match.

Upon the Shirais' return to Japan, Triple Tails made its debut as a unit for Pro Wrestling Wave on December 19, defeating Cherry, Gami and Tomoka Nakagawa in the six-woman tag team main event.

[48] On January 29, 2011, the Shirais made their debuts for Smash, when the Triple Tails stable attacked Yusuke Kodama and Makoto after their matches, with the trio being both times chased out of the ring by Tajiri.

[52] In March, Triple Tails took part in Osaka Pro Wrestling's Spring Samba Series, going undefeated in six-person tag team matches for the duration of the tour.

[61] On July 23, Triple Tails held a press conference to announce that, following the group's third self-produced event on September 18, Io was leaving the stable in order to pursue a singles career.

[68][69] After the break up of Triple Tails, Shirai continued making semi-regular appearances for Osaka Pro Wrestling, forming a partnership with male wrestler Hayata,[70][71][72] whom she would refer to as her "big brother".

[75] Initially, Shirai announced that she was leaving Union Pro following her loss, but eventually came back to form a partnership with Ken Ohka, who had now accepted his role as her inferior.

[77] On November 23, Shirai and Kana defeated Ayako Hamada and Shuu Shibutani in the finals to win the Osaka Joshi Pro Wrestling Tag Team Tournament.

[80] On the third and final night of the tour in Manhattan, New York, Shirai, Aja Kong and Tsubasa Kuragaki defeated Hanako Nakamori, Manami Toyota and Sawako Shimono in a six-woman tag team match.

[82] At a Pro Wrestling Wave event on February 1, Ayumi Kurihara, Mika Iida and Shuu Shibutani joined forces with Shirai and Kana, turning Triple Tails.S from a tag team once again into a stable.

[84] On February 11, Shirai began working regularly for Oz Academy, defeating Hiroyo Matsumoto, a member of the villainous Seikigun, in her return match to the promotion.

[85] On February 26, Shirai was defeated by Seikigun leader Mayumi Ozaki in a tryout match and afterwards agreed to join her stable, noting that they "had a lot of things in common".

Afterwards, Shirai agreed to join Black Dahlia at the request of Ohata, who was trying to bring down the average age of her group, but also wanted to remain a member of White Tails.

[112][113][114] Following her win, Shirai turned down Miyako Matsumoto's challenge for the title and stated that she instead wanted to defend it against Tsukasa Fujimoto, whom she dubbed "the face of Ice Ribbon".

[128][129] On January 13, 2013, Shirai received her first shot at the Oz Academy Openweight Championship in a match, where she was defeated by the defending champion, fellow Seikigun member Chikayo Nagashima.

[130] On January 30, Shirai entered a tournament contested for the vacant Triangle Ribbon Championship, defeating Aoi Kizuki and Hikaru Shida in her first round three-way match.

[152] On July 12, the White Tails stable produced their final event before the group's dissolution, during which Shirai defeated the soon-to-retire Ayumi Kurihara in a singles match.

Post-match, the now unmasked Hiroshi Fukuda apologized for the stable's past actions and both he and Shirai were welcomed back to Union Pro by the promotion's official representative Naomi Susan.

Picking up wins over the likes of Hiroshi Fukuda, Masayuki Mitomi and Menso～re Oyaji, Shirai earned the right to collaborate with AV actresses such as Rika Seibi, Ryu Mizusaki and Tsubasa Amami.

[187][188] On August 1, Shirai held a press conference to announce that on September 11 she would be producing her own event at Shinjuku Face under the banner of "M.I.O" (Mission in Odate), which would feature her wrestling her first deathmatch.

[197] On October 1, Shirai and Ohata defeated Dynamite Kansai and Fairy Nipponbashi to advance to the semifinals of the tournament, where, later that same event, they wrestled Kyoko Kimura and Tomoka Nakagawa to a fifteen-minute time limit draw.

[215] In early 2015, Shirai and Misaki Ohata received two shots at the Wave Tag Team Championship, but were both times defeated by the defending champions, Las Aventureras (Ayako Hamada and Yuu Yamagata).

Following outside interference from Tomoka Nakagawa, Shirai was pinned by Kobayashi and, as a result, relinquished the Oz Academy Openweight Championship, ending her reign at only four hours and two minutes.

Finally, she wrestled in a six-woman tag team main event, where she, Misaki Ohata and Tsukasa Fujimoto were defeated by Hiroe Nagahama, Risa Sera and Tsukushi, who pinned her to end her career.

[6] On December 15, 2015, it was announced that Shirai would start working as a referee under the ring name Mio, written in Roman script and stylized in all capital letters.