The Asian champions qualified for the finals in Brazil when playmaker Keisuke Honda scored an injury-time penalty to claim a 1-1 draw with Australia in Saitama on Tuesday.
"We want to win on the world stage... ach and every player on this team needs more determination and willpower," Manchester United midfielder Kagawa told reporters on Wednesday.
"We've got a lot of talented players playing their club football overseas now, but we all need to be more assertive when we play for Japan."
While he was happy with the team's unity, Kagawa felt the Blue Samurai needed to show more character on the field.
"One of our strengths is team work, but we can't win on that alone. We need more personality, character on the team. Team work may sound good, but it's just not enough," he added.
"We need more players to be selfish, more players who want it... like Keisuke [Honda].
"And the fact that we haven't been able to win when Keisuke isn't around says everything. I think everyone on the team feels the same way."
Japan will play their final qualifier against Iraq in Doha on Tuesday before making the trip to Brazil to play in the Confederations Cup.
Alberto Zaccheroni's men will get enough international exposure to raise their game after the country's football association confirmed six friendlies, scheduled between September and November.
Japan will host Guatemala on September 6, followed by a game four days later in Yokohama against Ghana. The team will tour Eastern Europe in October, facing Serbia and Belarus while two more matches are scheduled in November.
"We've got to aim high, can't allow ourselves to become complacent," Zaccheroni said. "We want to do well at the World Cup, and the Confederations Cup will be a great place to find out where we are in the pecking order of world football.
"In Europe, where I come from, a lot of people think the world never changes. I don't. I want to show we're on a par with the world's best teams on football's biggest stage."
