The Black Sticks women have made an opening statement by stunning Argentina to put their counterparts on notice at the Tokyo Olympics.
The Black Sticks men followed suit later in the day.
Argentina, world No 2, were heavily favoured to account for a depleted New Zealand side in the searing heat.
Yet with defensive resilience and clinical attacking execution sixth-ranked New Zealand upset the South Americans 3-0 to make the best possible start to their Games campaign.
That the victory was achieved without captain Stacey Michelsen and vice-captain Samantha Charlton, as well as legend Kayla Whitelock, who tore her ACL on the eve of attending her fifth Olympics, magnifies the sense of satisfaction for the young brigade.
Three second-half goals - Hope Ralph and Kelsey Smith scoring from penalty corners and a brilliant strike from Holly Pearson to claim her first international goal – sealed victory, but the Black Sticks were even more impressive on defence.
Goal keeper Grace O'Hanlon kept a clean sheet to rebuff six penalty corners. Chasing the game, Argentina piled on the pressure in the final quarter but O'Hanlon held firm to increasingly build frustration.
In a gruelling tournament that forces teams to play five matches in six days, the Black Sticks are now well placed to be one of four sides to progress from their pool.
The Black Sticks, Commonwealth Games champions on the Gold Coast three years ago, next meet world No 14 and hosts Japan on Monday (11:45pm).
Australia (second ranked), Spain (seventh) and China (10th) are also in New Zealand's pool.
Later, the Black Sticks men got their Olympic campaign right back on track, edging a seven-goal thriller against Spain.
Jacob Smith's goal three minutes from fulltime proved the winner in an action-packed encounter in Tokyo, helping New Zealand to a 4-3 victory.
The Black Sticks had suffered a 3-2 defeat by India in their first game on Saturday and their second clash was similarly hectic.
The Kiwis held a 2-1 lead at the halftime break, courtesy of a smashing strike from Stephen Jenness and a scrambled finish from skipper Blair Tarrant.
But Spain charged back into the match in the third quarter as the Black Sticks looked set to throw away another lead, before Kane Russell equalised with a perfect low drag-flick and Smith was in the right place at the right time to play hero.
The Black Sticks men have a day off before playing Japan on Tuesday.
- Additional reporting Kris Shannon