"From a defending perspective we want to make sure the level of pressure we exert on the opposition is where it needs to be.
"We've been a little bit inconsistent with that sometimes this year and it's in those weaker moments when you're going to get exploited by these top level teams. We know we're going to be tested for 90 minutes so it's going to be a good test for that.
"From an in-possession perspective we've been working a lot on getting the ball into positions where we can score goals. We've been doing a lot of work in Auckland on that and we've been doing that since we got here.
"We're just trying to get a better shared understanding about how we can unpick these teams because no team we're going to play between now and the end of the World Cup is going to give us anything, we're going to have to take it."
Readings says the squad are well-placed to achieve that aim on Sunday with a slick build-up in Japan since the team arrived earlier this week.
"The trainings have been excellent so far. Everyone single one has been at a high standard and it's been great preparation for the game.
"Maybe we've seen a little bit more intensity and energy because of the excitement of what everyone has been working for over the last two and bit years since we've had the support from High Performance Sport New Zealand. It's almost now come to a point where everyone is just dying to show people on the world stage what we can do.
"If we can hurt Japan as often as we'd like to, we know we can hurt the teams we're going to play in the group stage and beyond at the World Cup."
Sunday's clash will be the fourth between the two sides since 2011 with a pair of 2-1 defeats bookending a 1-1 draw.
If selected, striker Amber Hearn will play in her 99th international match for the Football Ferns while Kirsty Yallop will bring up 90 caps with an appearance on Sunday.
Football Ferns v Japan
Marugame Stadium, Kagawa, Japan
Sunday 24 May, 7pm (10pm NZ time)
LIVE SKY Sport 1
New Zealand (from): 1. Erin Nayler (GK), 2. Ria Percival, 3. Anna Green, 4. Katie Duncan, 5. Abby Erceg (capt), 6. Rebekah Stott, 7. Ali Riley, 8. Jasmine Pereira, 9. Amber Hearn, 10. Sarah Gregorius, 11. Kirsty Yallop, 12. Betsy Hassett, 13. Rosie White, 14. Katie Bowen, 15. Meikayla Moore, 16. Annalie Longo, 17. Hannah Wilkinson, 18. CJ Bott, 19. Evie Millynn, 20. Daisy Cleverley, 21. Rebecca Rolls (GK), 22. Emma Kete, 23. Cushla Lichtwark (GK)
Coach: Tony Readings