Strikers Mana Iwabuchi and Yuika Sugasawa were on the scoresheet as Japan got their women's World Cup campaign back on track with a 2-1 victory over Scotland in Rennes on Friday.
Japan, champions in 2011 and finalists four years ago, were coming off a uninspiring goalless draw with lowly-ranked Argentina in their opener but looked much sharper in the attacking third against Scotland.
They got a breakthrough when striker Iwabuchi controlled a poor headed clearance from Scotland captain Rachel Corsie before unleashing a powerful strike high into the net from 20 metres.
Sugasawa doubled Japan's lead from the spot in the 37th minute after another defensive error from Corsie, who was penalised for tugging back the forward in the box.
It was one-way traffic at Roazhon Park as Japan continued to launch wave after wave of attacks, with midfielder Hina Sugita coming closest when her shot crashed into the crossbar just before half-time.
Scotland responded with a physical approach going forward in the second half and pulled one back through a curling effort from substitute Lana Clelland but Japan held on to the advantage to seal their first win of the tournament.
"It was a must-win game and, although there were tough moments, we're very happy to get the win," Japan coach Asako Takakura said.
"We had to be aggressive and score goals, and that's what we did. We didn't show our true selves in the first game at this tournament but this was a lot more like the true Japan."
It was a second consecutive defeat for World Cup debutants Scotland, following a 2-1 loss to England in their opening match.
Shelley Kerr's team will now need a win over Argentina in their final group stage contest on Wednesday to have a chance of progressing to the knockout stage as one of the four best third-placed sides.
"We conceded two bad goals through mistakes. Take those mistakes away and the game's a lot closer," Kerr said.
"I think we saw the real Japan today -- their movement was incredible, as we knew it would be. But for most of the second half we were terrific and, again, we finished very strongly.
"I'm immensely proud of the players. We need to build on that second half, rest up and get ready for the match against Argentina."
Japan, ranked seventh in the world, will go into their game against England next week with a chance of topping Group D.