[9] Kubota fought once more in J-Girls in the World Queen Tournament and defeated Mika Nagai by decision on November 4, 2007 (2007-11-04).
On June 1, 2008 (2008-06-01), Kubota fought to a draw with MMA fighter Miku Matsumoto in the Deep promotion in a kickboxing match at ClubDEEP Toyama Barbarian Festival 7.
[14] Kubota's next fight, her second professional loss, came in a rematch against Miku Matsumoto at the Shoot Boxing World Tournament 2008 on November 24, 2008 (2008-11-24).
She was defeated via extra-round split decision against South Korean Muay Thai kickboxer Su Jeong Lim.
[36][37] As a result, Kubota faced J-Girls rising talent Erika Kamimura in an exhibition match in which Rena was knocked down once by her younger opponent in a single three-minute round, which surprised fans and pundits alike.
[36][37][38] Kubota faced Ai Takahashi again in a five-round title fight at Shoot Boxing 2011 Act 3 on June 5, 2011 (2011-06-05).
Nevertheless, Rena won the match when she delivered a devastating punch to Sor Aree's stomach in round two which caused her to collapse to the mat.
Flat on her back and holding her stomach in agony, Sor Aree was not able to continue and Rena won the match.
This would be the second time that Rena's powerful attacks have left an opponent in so much pain that they are not able to get up and not able to continue the match.
She defeated Kim Townsend, Seo Hee Ham and Mei Yamaguchi in succession to become the 2012 Shoot Boxing Girls S-Cup tournament champion.
[50][51] Kubota returned to face Taiwanese fighter Du Peiling at Shoot Boxing 2013: Act 2 on April 20, 2013 (2013-04-20).
[54][55][56] On June 23, 2013 (2013-06-23), it was announced that Kubota would face Lorena Klijn during the 2013 Shoot Boxing Girls S-Cup Japan Midsummer Festival event on August 3, 2013 (2013-08-03).
[59][60] On November 16, 2013 (2013-11-16), at Shoot Boxing Battle Summit: Ground Zero Tokyo 2013, Kubota defeated late replacement opponent Maylee Won.
[63] Kubota was scheduled to fight Yuri Kim at Shoot Boxing 2013: Tomohiro Oikawa Retirement Event on December 23, 2013.
[66] Kubota participated in the 2014 Shoot Boxing Girls S-Cup tournament, and faced Simone van Dommelen in the quarterfinals.
[73] Kubota made her first title defense against Klaudia Pawicka at Shoot Boxing Girls S-Cup 2016, on July 7, 2016.
[74] She won the fight by a third-round technical knockout, forcing her opponent's corner to throw in the towel mid-way through the round.
[75] Kubota's next fight was a non-title bout against Kinberly Novaes at Shoot Boxing World Tournament S-Cup 2016, on November 16, 2016.
[77] Kubota fought Jleana Valentino in a non-title bout at Shoot Boxing Girl's S-Cup 2017, on July 7, 2017.
[79] Kubota made her mixed martial arts debut against a fellow debutante in Jleana Valentino at Rizin World Grand-Prix 2015: Part 2 - Iza on December 31, 2015.
[82] Kubota won the fight by a first-round submission, locking in a guillotine choke with ten seconds left in the round.
[86] She won the fight by a first-round technical knockout, dropping Perjés with a liver punch at the 2:48 minute mark.
She was scheduled to face the former King of the Cage Atomweight champion Andy Nguyen in the quarterfinal bout at Rizin World Grand Prix 2017: Opening Round - Part 2 on October 15, 2017.
[89] Advancing to the semifinals, Kubota faced Irene Cabello Rivera at Rizin World Grand-Prix 2017: Final Round on December 31, 2017.
[101] On October 7, Rizin president Sakakibara revealed that Ram withdrew from the bout after suffering a concussion in training.
[104] Kubota won by a third-round technical knockout, stopping her opponent with ground and pound with just 18 seconds left in the fight.
[113] Kubota was expected to face Seika Izawa in the tournament semifinals, but was forced to withdraw due to injury, as her orbital bone fracture hadn't yet healed.