Mayumi Ozaki
On December 23, Kaoru and Mayumi Ozaki faced each other in their first singles match, a "Serial Killing" hardcore match, where a wrestler would have to earn two back-to-back pinfall or submission victories to win the match. In a match, which featured outside interference from Ozaki-gun, Kaoru won the first and third falls, before submitting to Ozaki in the fourth fall. Finally, in the fifth fall of the match, Ozaki dropped Kaoru with a brainbuster off a ladder through a barbed-wire board to win the fall and the match. In order to reduce Ozaki-gun's numbers advantage over her, Kaoru began teaming with Jungle Jack 21 in 2010, though not officially joining the stable. After defeating Ozaki-gun member Yumi Ohka with Mayumi Ozaki's signature "Ozakick" on May 16, Kaoru defeated another former stablemate, Takako Inoue, on June 13 to become the number one contender to the Oz Academy Openweight Championship. On July 11, Kaoru defeated Carlos Amano to win the Oz Academy Openweight Championship, becoming the promotion's top champion. She made her first title defense on August 22, defeating Mayumi Ozaki in a Last Woman Standing match. Her second defense took place on November 3, when she defeated Takako Inoue. On February 19, 2011, Kaoru made her third successful defense, defeating Jungle Jack 21 member Ran Yu-Yu. On April 10, Kaoru, Aja Kong and Mayumi Ozaki faced each other in a three-way two-fall match, where Kaoru put her title and Kong and Ozaki the futures of their respective stables on the line. During the first fall, Kaoru fractured her calcaneus when diving out of the ring onto Kong and was unable to continue the match, resulting in the referee declaring the match a no contest and stripping Kaoru of the Oz Academy Openweight Championship, ending her reign at 273 days. Kaoru underwent surgery four days later. Her recovery was slowed down by her developing an osteomyelitis.