Crystal Palace forward Daichi Kamada warned his Japan teammates that tougher tests lie ahead after rounding off their successful World Cup qualifying campaign with a 6-0 thrashing of Indonesia on Tuesday.
Kamada, an FA Cup winner with Palace in England this season, struck twice in the first half as already qualified Japan finished the campaign as Group C winners, scoring 30 goals in their 10 matches.
Takefusa Kubo, Ryoya Morishita, Shuto Machino and substitute Mao Hosoya were also on target against Patrick Kluivert's Indonesia, who finished fourth in the group.
Japan coach Hajime Moriyasu has set the ambitious target of winning next year's World Cup in the United States, Canada and Mexico.
His side will play friendlies against teams from outside Asia over the next 12 months and Kamada is looking to learn from the experience.
"Playing against Asian teams and against the kind of European teams who will be at the World Cup is totally different," said the 28-year-old.
"As we play these games, we will start to see a lot of areas where we need to improve. We need to come together as a team and overcome these problems when they crop up."
Japan have already lined up away friendlies against Mexico and the US in September and will face four as yet unnamed opponents at home before the end of the year.
Moriyasu said his players need to keep improving "in all departments" and praised their attitude against Indonesia.
"The challenge for the players is to break past their limits and grow," he said.
"They did that in training and in the game, where they were never satisfied and always looking for the next goal and the next chance, which is great to see."
Japan lost their unbeaten qualifying record in a 1-0 defeat away to Australia last week, with Moriyasu fielding an experimental line-up with qualification already in the bag.
He started with two more debutants against Indonesia, handing first caps to defender Junnosuke Suzuki and winger Shunsuke Mito.
Kamada opened the scoring in the 15th minute, heading home from a Mito cross.
The Palace forward turned provider for his team's second, combining with Kubo before the Real Sociedad man fired past Indonesia goalkeeper Emil Audero.
Kamada scored Japan's third on the stroke of halftime, waltzing through the Indonesia defence before tucking the ball over Audero.
Morishita volleyed home at the back post in the 55th minute for his first international goal.
Machino and Hosoya also got on the scoresheet as Japan continued to squeeze Indonesia until the final whistle.
Indonesia, who were backed by a large travelling support in Japan, advance to a further round with five other teams to decide two more Asian qualifiers for next year's tournament in the United States, Canada and Mexico.
