Alberto Zaccheroni's men were beaten by the Ivory Coast in their opening fixture, as they surrendered a lead to lose 2-1.
With Greece also suffering defeat in their first fixture in Brazil, via a 3-0 loss against Colombia, Kagawa feels that both teams will need to go for broke in Natal later this week.
The Manchester United man lamented Japan's inability to take anything from their opening game and says there is no room for caution in their remaining fixtures.
"We were never really in control of the game (against Ivory Coast)," he told AFP.
"Greece will attack us because they lost too. We have no option but to attack."
Japan have made it out of the group stage in two of their last four World Cup appearances - reaching the last 16 in both 2002 and 2010.
