Ryohei Arai was the top qualifier for the men's javelin final at the world athletics championships on Monday.
Needing 83.00 meters to automatically qualify for Wednesday's final, Arai threw a personal season-best 84.66, 1.34 ahead of Argentina's Braian Toledo.
Arai, who holds the second-longest throw ever by a Japanese at 86.83, believes he has put himself in a position to become Japan's first medalist of these championships.
"I've got a lot more in me. I can keep stretching my record," he said. "I see a medal now, and I'm just going to go all out in the final."
Chisato Fukushima failed to make the women's 100-meter final after finishing seventh in her heat in 11.32.
For the men's 200 qualifying on Tuesday, 16-year-old Japanese phenom Hakim Sani Brown was drawn in the same heat as Justin Gatlin, who narrowly lost to Usain Bolt in the 100 final.
Sani Brown won the 200 in 20.34 at last month's world youth championships, breaking the mark Bolt set 12 years ago.