They were so dominant in the final that their opponents only managed to score in the final period.
Japan won the Asian Youth Water Polo Championship boys' title in style last night by thrashing Iran 12-3 at the Toa Payoh Swimming Complex.
The bigger-sized Iranians simply had no answer for their opponents' speedy counter-attacks down the flanks, launched by laser-guided passes from goalkeeper Kazuki Hashimoto.
Kohei Inaba scored three in the rout to finish the boys' tournament as the top scorer with 31 goals, but it was teammate Shotaro Yamada who starred in the final with four goals.
Coach Yuzuru Machida said: "I didn't expect such a big scoreline; it was a good surprise and it was because of our defence, which kept improving with each game in the tournament."
With all aged 17 and under, some of the Japanese players in this squad may go on to represent their country at the 2020 Olympics, which Tokyo will host. Machida said: "We are keen on developing them towards that goal... we are targeting to reach the semi-finals in 2020 and these boys will move up an integrated development system - comprising various age-groups - in the coming years."
But it was a bittersweet day for Japan, as the girls' team fell 11-5 to China in the final.
The Japanese (right, in blue) trailed 4-2 after the first eight-minute period and never caught up, with the Chinese (in red) shutting them out in the final period.