Hiroyo Matsumoto
Kato finally returned to the ring at an independent event produced by Chigusa Nagayo on October 1, 2006. Kato then began working regularly for the Oz Academy promotion, which featured many other former Gaea Japan wrestlers. On May 25, 2008, Kato made her Mexican debut for Lucha Libre AAA World Wide (AAA), taking part in a five-way elimination Reina de Reinas Tournament match, from which she was eliminated by Martha Villalobos. The following July, Kato and Chikayo Nagashima made it to the finals of a tournament to determine the inaugural Oz Academy Tag Team Champions, before losing to Carlos Amano and Dynamite Kansai. Kato and Nagashima eventually won the title from Aja Kong and Hiroyo Matsumoto on February 22, 2009. During the next eighteen months, Kato and Nagashima won the title two more times, becoming three-time champions together. Kato won the title for the fourth time on January 15, 2012, this time teaming with Aja Kong. After a seven-month reign, they lost the title to Akino and Ayumi Kurihara. On January 12, 2014, Kato received a shot at the Oz Academy Openweight Championship, but was defeated by the defending champion, Akino. The following June, Kato underwent a shoulder surgery, which would sideline her for an estimated six months. She returned to the ring on January 11, 2015. On February 8, Kato formed a new stable with Akino, Kagetsu and Kaho Kobayashi, which was on April 15 named "Mission K4" (MK4). On August 23, Kato won the first singles title of her twenty-year career, when she defeated Hiroyo Matsumoto in a Last Woman Standing match to win the vacant Oz Academy Openweight Championship. On October 10, Kato returned to the United States, when she made her debut for Shimmer Women Athletes, taking part in their two-day tenth anniversary weekend. After four successful title defenses, Kato was stripped of the Oz Academy Openweight Championship on April 24, 2016, when her defense against Hiroyo Matsumoto ended in a no contest. On July 18, Kato defeated Mayumi Ozaki to regain the vacant Oz Academy Openweight Championship. On November 13 at Oz Academy's 20th anniversary event, Kato lost the Oz Academy Openweight Championship to Hiroyo Matsumoto in her second defense.