Mai Yamamoto led with eight points, including a critical two-pointer with about a minute left to put her team ahead.

Japan advanced to 5-2 and second place in the pool round.

Japan head coach Torsten Loibl said the victory was important to show his team is ready for the knockout stages.

“It’s not important to win or lose, but it’s a message,” he said from the stands moments after the final whistle sounded.

A late penalty gave Team USA 1.1 seconds to tie the game with a two-pointer.

But Japan’s Stephanie Mawuli blocked an attempt from Las Vegas Aces guard Kelsey Plum, sealing the 20-18 upset.

A light rain fell upon the Aomi Urban Sports Park in Tokyo as a typhoon approached Japan’s main island, a respite from three days of searing heat.

After the final pool matches this afternoon, four teams will move ahead to the quarterfinal matches in the evening.

The US women and the top-seeded Serbian men have secured their spots in the semifinals tomorrow, which will also feature the medal matches.

With its Olympic debut, 3×3 is looking to boost its global profile as a faster-paced, more compact alternative to traditional basketball.

Enhancing that atmosphere, DJs play hip-hop music throughout competition in 3×3 games, in keeping with the sport’s urban roots.