Complex sentence: Yoshida started competing internationally as a cadet, in 1998, in the 52 kg category, and by 2002, when she moved to seniors, reached the 59 kg division.
Split into simpler sentences: Yoshida started competing internationally as a cadet, in 1998, in the 52 kg category. By 2002, when she moved to seniors, she competed in the 59 kg division.