He moved to Tokyo during summer vacation, and entered the Kyoei boxing gym to begin serious training.

On June 4, 2004, Sakata fought Lorenzo Parra for the WBA Flyweight title at the Ariake Coliseum in Tokyo, Japan, but lost by 12-round decision.

He marked five straight wins after his losses against Parra, and fought Roberto Vasquez in Paris, France, for the WBA Flyweight interim title on December 2, 2006.

He suffered a knockdown in the 5th round, but fought back hard in the second half, and Vasquez barely managed to keep his title with a 2-1 split decision.

The WBA decided to hold the title match with a bantamweight limit (118 lb/53 kg), and Parra was introduced as the former champion for the fight.