Tsuji spent the majority of her career competing in the now-defunct Smackgirl promotion. She debuted with defunct promotion Ax on in the event Ax - Vol. 2: We Want To Shine with a victory by submission over the previously undefeated Ikuma Hoshino, who at the time was the most accomplished female Japanese MMA fighter. This would be Hoshino's only loss in her MMA career. Tsuji debuted in Smackgirl at Smackgirl - Royal Smack 2002 on, defeating Hiromi Oka by submission due to a rear naked choke. Including her debut, Tsuji would go on a winning streak of 8 consecutive victories; in the process winning the Smackgirl Japan 2002 Cup Middleweight Tournament on. In her ninth professional bout, she faced Brazilian fighter Ana Michelle Tavares. Tavares defeated Tsuji with a triangle armbar submission in Tsuji's debut for the Deep promotion at Deep - 11th Impact on. In this match, Tsuji injured her left shoulder. This was Tsuji's first defeat in MMA. She avenged this loss years later. After her first loss, Tsuji won her next four fights and then faced Hisae Watanabe at Smackgirl - Road to Dynamic!! for the first Smackgirl Lightweight Championship on. Tsuji won the title after defeating Watanabe by armbar at 3:51 of the first round. She would go on to successfully defend the title five times until the demise of the Smackgirl promotion. On, Tsuji would get the chance to face Tavares again. At the event Smackgirl - Queens' Hottest Summer, Tsuji was able to avenge her only loss at the time by defeating Tavares via KO at 4:47 of the first round. After defending her title for the last time against South KoreanSeo Hee Ham, Tsuji debuted in Valkyrie at the promotion's inaugural event Valkyrie 1 on, where she defeated Mei Yamaguchi by decision. Tsuji became the first Valkyrie Featherweight Champion on by defeating American fighter Kate Martinez. Her 14-fight winning streak came to an end on when she rematched Mei Yamaguchi, who this time was able to defeat Tsuji with a rear-naked choke in only 76 seconds. This was just the second time that Tsuji was defeated and the first time that she was defeated by a fellow Japanese fighter. This is considered one of the biggest upsets in the history of women's mixed martial arts. Having recovered from surgery on her knee and shoulder, Tsuji returned to MMA in a Jewels vs. Valkyrie bout against Saori Ishioka at Jewels 15th Ring on in Tokyo, Japan. She defeated Ishioka by unanimous decision. Tsuji faced Ayaka Hamasaki in a Jewels lightweight title fight at Jewels 19th Ring on in Osaka, Japan. She was defeated by submission due to a kimura in the first round. On, Tsuji faced Hyo Kyung Song at Deep Osaka Impact 2012. She defeated Song by technical submission due to an armbar in the first round.
