Watanabe entered the Saitamasakaechugakko Koto school, and won the singles title at the national junior championships, also placed third in the doubles event.

[6] Koki Watanabe celebrated a significant milestone in his badminton career by winning his first Super 500 title at the 2024 Canada Open.

Watanabe expressed his satisfaction with this achievement and emphasized the importance of staying focused and taking one step at a time to reach his goals.

In the final match, Watanabe faced Alex Lanier, the defending champion from 2022.

Lanier admitted that he ran out of energy in the third game, which allowed Watanabe to dominate and secure the title.