Competing in the extra-lightweight (48 kg) class, she won a record seven world titles and five Olympic medals including two golds at Sydney 2000 and Athens 2004.

[2] Standing at 1.46 m (4 ft 9 in), Tani fought in the extra-lightweight (48 kg) division her whole career and, unlike many of her opponents, she never had to cut weight before a competition.

[3] At Sydney 2000, she had a tough semi-final against North Korea's Cha Hyon-hyang, but she left no chance to her opponent in the final, Lyubov Bruletova of Russia.

[9] Four years later in Athens, she scored a series of ippon-victories to reach the final,[10] in which she dominated France's Frédérique Jossinet, taking an early koka lead that she confirmed with a waza-ari in the last seconds of the fight.

[5] In Beijing in 2008, she saw her hopes of a third-straight gold evaporate when judges awarded penalty points to Romania's Alina Dumitru after both competitors failed to show much aggression.

Looking stunned, Tani fought desperately after the final controversial penalty call, but with only seconds left she had no time to mount an attack.

The selection prompted Philip Brasor, media commentator for the Japan Times to ask "...maybe Tani is the better choice, but why have qualifying bouts in the first place?".

Tani followed in the footsteps of Kaori Yamaguchi, who in 1984 had become the first Japanese woman to ever win a world championship – the sport had long been a male preserve.

When Tani represented Japan in Barcelona, she was viewed by the Japanese public as a real-life Yawara and was soon nicknamed Yawara-chan or Tawara.

[citation needed] Tani is credited for the boom in women's judo witnessed by Japan in the 1990s, leading to the rise of a new generation of competitors.

Because she did not let her marriage put an end to her sporting career, and won her last world title as a young mother, she is also viewed as a symbol of the changing role of women in Japanese society.