Junichi Inamoto was the hero of Japan on Sunday, scoring the winner as the co-hosts beat Russia 1-0 after a storming second half to record their first ever victory in a World Cup finals.
The midfielder, who scored in Japan's opening 2-2 draw with Belgium last Tuesday, fired high into the net from close range after 51 minutes to send the 66,000 crowd at Yokohama's huge International stadium into rapture.
The deserved victory -- midfielder Hidetoshi Nakata also hit the bar with a piledriver -- lifted Philippe Troussier's side to the top of group H and kept them on course to reach the second round for the first time.
Japan have four points from two games, one more than Russia, who were a major disappointment in Sunday's game, which warmed up after a tepid first half. Belgium, who play Tunisia on Monday, have one point, with the north Africans on none.
In their first appearance in the finals in 1998 in France Japan lost all three group games and went home after the first round, having scored just one goal.
Hidetoshi Nakata should have put Troussier's side, who were without captain Ryuzo Morioka through injury, in front after 27 minutes but fired wastefully over the bar when the ball fell to him 12 metres out.
Russia offered little, although 19-year-old Marat Izmailov looked lively and almost scored after 15 minutes when he curled a delightful 20-metre effort just wide of Seigo Narazaki's far post.
Romantsev, who did not risk his unfit playmaker Alexander Mostovoi, brought on lively 18-year-old Dmitry Sychev at the start of the second half, making the combined age of his strikers just 37 years.
But it was Japan who struck the only goal. Koji Nakata played a diagonal ball into the penalty area that Atsushi Yanagisawa diverted into Inamoto's path and the midfielder took one touch before slamming the ball into the net past Ruslan Nigmatullin.
Romantsev introduced his most experienced striker, Vladimir Beschastnykh but the out-of-form Russian immediately contrived a shocking miss, hitting the side-netting when he should have scored after rounding the goalkeeper.
Japan fully merited their win, though, and Hidetoshi Nakata almost made it 2-0 after 71 minutes, rattling the bar with a ferocious 25-metre drive.