Vilda is confident La Roja will bounce back from that bitter disappointment to be victorious in their group of 16 game on Saturday against Switzerland.
"The defeat of the other day, we haven't forgotten about it and we will not forget about it. These types of defeats leave a deep mark upon us, but they are also necessary in the evolutionary development of the team and process of growth," Vilda said at a press conference on Friday.
Sixth-ranked Spain kicked off their campaign by beating Zambia and Costa Rica by a combined 8-0. But Japan, who finished atop Group C, put on a counter-attacking clinic against Spain, who advanced to the final 16 for the second time in three appearances at the global tournament.
"We've made a detailed analysis of everything that happened against Japan as a team, individually, the behaviour of the players, the goals, the positive aspects and negative aspects," Vilda said.
"Of course, one of the aspects that we have to improve is to be ready for the counter-attacks. It's a question of defensive positioning, the compact structure that will help us to be sure about defence in all situations."
Switzerland, ranked 20th, kept a clean sheet in the group stage with a 2-0 win over the Philippines and scoreless draws against Norway and New Zealand.
"Switzerland have something very valuable that in three games no one scored a goal against them. That means that the defence is very solid," Vilda said.
Spain, who boast two-time Ballon d'Or winner Alexia Putellas, have been mired in crisis in the World Cup buildup, with 15 players threatening to quit last September in the wake of their quarter-final exit at the 2022 Euros if Vilda was not sacked. The federation backed the longtime coach.
Vilda shouldered the blame for the Japan debacle, the squad's worst loss in 11 years.
"I am the coach and I take responsibility for this defeat," he said after the match.
The coach believes the World Cup has yet to see the best of his side, and he is confident of a strong performance on Saturday at Auckland's Eden Park.
"If I didn't feel that we could change the situation, I wouldn't be sitting here," Vilda said.
"I'm quite sure that they are going to play extremely well, and the technical team, all the players, the whole team, of course we are ready. I, of course, want to reach the quarter-finals and that would be a historical thing for us."