Nagano debuted in MMA in an exhibition match against
Megumi Yabushita at
Smackgirl: F 2006 on . She made her professional debut against
Megumi Fujii and lost via submission (triangle choke) at
Smackgirl: Starting Over at
Korakuen Hall on . After winning her next fight by
split decision and losing her third by decision, she went on to win her following three fights by submission (armbar). In the process, she won the 2009 Rough Stone Grand Prix 54 kg & under tournament after defeating Yoko Kagoshima in the tournament final. Haga dominated the whole fight, earning a unanimous decision win. The loss was so devastating that Nagano was in tears even before the fight ended. Nagano managed to avenge this loss in the Jewels Lightweight (115 lb) Queen Tournament Opening Round by defeating Haga with an armbar submission at
Jewels 9th Ring on . She faced
Seo Hee Ham in the tournament semi-finals on at
Jewels 11th Ring and was defeated by split decision after two rounds. Nagano was scheduled to face Emi Murata at
Jewels 12th Ring on in
Tokyo, Japan, but the event was cancelled after the
Tōhoku earthquake and tsunami earlier in the day. She then faced Murata at
Jewels 14th Ring on and defeated Murata by submission in the first round. Nagano rematched
Megumi Fujii at
Jewels 15th Ring on . She was defeated by unanimous decision. Nagano faced
Mei Yamaguchi at
Jewels 17th Ring on . She was defeated by split decision. Nagano then faced
Emi Fujino at
Jewels 18th Ring on . She lost the fight by unanimous decision. On , Nagano faced Anna Saito at
Jewels 19th Ring in Osaka, Japan. She won the fight by submission due to an armbar in the first round. Nagano's next fight took place on when she faced
Tomo Maesawa at
Jewels 21st Ring. She defeated Maesawa by technical submission due to an armbar in the second round. On , Nagano competed outside Japan for the first time when she faced
Alexandra Chambers at
Brace For War 17 in Australia. She was defeated by TKO early in the first round. Nagano faced Rina Tomita for a third time at
Jewels 22nd Ring on . The fight was Tomita's retirement match. Nagano defeated Tomita by submission due to an armbar in the first round. Nagano next faced Emi Tomimatsu at
Jewels 23rd Ring on . She won the fight by unanimous decision. On , Nagano faced Takumi Umehara at
Jewels 24th Ring. She defeated Umehara by submission due to a rear-naked choke in the first round. Nagano next faced Akiko Naito in Naito's retirement fight at
Deep Jewels 1 on . She defeated Naito by submission due to an armbar in the first round. In a rematch at
Deep Jewels 2 on , Nagano faced Emi Tomimatsu in the opening round of the Deep Jewels lightweight title tournament. She was defeated by unanimous decision. On December 28, 2013, Nagano announced that she was retiring from MMA the following February. However, on February 6, Nagano announced she was pregnant and would have to pull out of her exhibition match with
Saori Ishioka. ==Professional wrestling career==