Japan star Ayumu Goromaru says the team are hungry to make the quarter-finals and won't be resting on their win over the Springboks.
Goromaru has scored 29 points through Japan's first two matches and his goal-kicking will be essential if Japan are to topple Samoa on Saturday.
"There are a few players we're marking and how we look after them will make the difference. They make you pay from mistakes and after kicks with a strong counter-attacking game," Goromaru said.
"We may have changed the history of rugby by beating South Africa in our first game but our target ultimately is to reach the last eight.
"So we must beat Samoa, no matter what."
Samoa will pose another physical challenge for Japan but after seeing off South Africa, Goromaru isn't concerned.
"I've had the opportunity to experience many things so they [Samoa] don't scare me," Goromaru added.
"But I think you'll see them trying to break the game wide open in the first half and we need to stop them at those points.
"We have to dig deep and speed up the game when they start to tire, play the type of rugby only Japan can play."