Japan showed they have the "guts" to compete at the World Cup, defender Yuto Nagatomo said Thursday, after the Blue Samurai stunned Spain to advance to the last 16.
Japan upset both Germany and Spain to finish top of Group E, digging deep to come from behind to grab gritty victories in both games.
Hajime Moriyasu's side will now face Croatia in the last 16 and Nagatomo believes they can pull off another shock against the 2018 World Cup finalists.
"No one in the world believed that Japan would finish top of this group -- no one," said Nagatomo.
"But we believed, and we believed during the game today. We showed the world what Japanese guts looks like."
Nagatomo said the game went "according to plan" despite Spain scoring an 11th-minute opener through Alvaro Morata.
Japan made it to half-time without conceding any more despite fierce Spanish pressure, and two goals from Ritsu Doan and Ao Tanaka early in the second half completed the turnaround.
"We knew there was a chance we would concede a goal, and we knew that if that happened and we fell to pieces and conceded another it would be a very difficult game," said Nagatomo.
"We were prepared for that situation and we held it together. Not one player fell apart."
- Mood shift -
Moriyasu came in for heavy criticism after Japan lost 1-0 to Costa Rica in their second game but Nagatomo said the coach stuck by his tactics against Spain despite the early setback.
"The manager didn't waver. And if the manager doesn't waver, the players don't either," said Nagatomo.
The game followed a similar pattern to Japan's 2-1 win over Germany, with two second-half goals changing the complexion of the game.
Defender Shogo Taniguchi, who was making his first appearance of the tournament, said "the atmosphere changed" when Doan's goal went in.
"It changed for us and it changed for the whole stadium," he said.
"It felt the same as it did in the game against Germany and we felt like we could go on and do it."
Japan will now face a Croatia side that went all the way to the final four years ago and dumped Belgium out of the tournament earlier on Thursday.
Nagatomo played alongside Marcelo Brozovic, Mateo Kovacic and Ivan Perisic at Inter Milan but he believes Japan can cope with their quality.
"They're world-class players and they also have Modric," he said.
"They're a team with a lot of talent but I definitely believe we can get past them. I believe our team has that power."
Nagatomo said he "felt the strength of Japanese football" in their performance against Spain.
"The fact that the game went according to plan and we got the win made me feel just how much Japanese football has grown," he said.