Japan will "fight like samurai" in Monday's World Cup last-16 clash with Croatia as they battle to reach the quarter-finals for the first time, defender Yuto Nagatomo said.

Japan reached the knockout round after stunning Germany and Spain to top Group E but they are not satisfied with what they have achieved so far in Qatar.

"Before battle, the samurai would polish their weapons and refine their technique, but if they were scared in battle, all that would count for nothing," the former Inter Milan left-back said Sunday.

"It's the same as football. Of course tactics and technique are important, but if we're scared, it doesn't matter how much we've trained over the past four years because our technique will be no use.

Japan have reached the last 16 at three previous World Cups but they have yet to make it as far as the quarter-finals.