Koroi’s score came with New Zealand and South Africa deadlocked at 21-21, with the All Blacks Sevens needing to win to make Sunday’s Cup quarter-finals in Cape Town.
They had trailed twice — first through Rosko Specman’s try and then Branco du Preez — but Sione Molia’s try was converted with one second remaining to set up the most enthralling of finishes.
“Tough old game out there,” New Zealand’s Dylan Collier said afterwards. “[It was a] big crowd, awesome atmosphere and we did well to come back. After last week we knew we had to lift our game.
“I think we knew what we wanted to do, we just had to go out there and make sure we did the basics right, and it just opened up for us at the end there.”
It sets up a quarter-final tie with Australia, who finished top of Pool D. South Africa will face Scotland, Fiji will take on Spain, and USA will be up against England.
New Zealand had suffered a scare earlier in the afternoon with a 21-17 defeat against Samoa. Tila Meloi’s last-minute try left the All Blacks Sevens on the brink of the Challenge Trophy.
Koroi’s heroics for New Zealand meant that Samoa finished third in the pool, having put the pressure on with a 33-12 victory over Zimbabwe. Tries from Stephan Hunduza and Tafadzwa Chitokwindo gave Zimbabwe hope but Samoa proved too strong.
South Africa were denied an unbeaten day with defeat to New Zealand. They began the day by coming from behind to defeat Samoa (22-12) before Siviwe Soyizwapi’s hat-trick helped the hosts to a 43-0 victory over neighbours Zimbabwe.
Spain provided the shock of the day by beating Argentina in their first game before qualifying for the Cup quarter-finals at the expense of the South American outfit.
Argentina led twice but two tries each for Javier Carrion and Pablo Fontes helped Spain to a 35-12 victory. A resounding 52-0 win over Japan put Spain on the brink of qualification before it was confirmed thanks to USA’s victory over Argentina.
USA needed a recovery in that match to end day one in Cape Town unbeaten. A win was all they required to qualify for the Cup quarter-finals but found themselves 14-7 down at the break with one minute to play with six men in the second half after Danny Barrett’s yellow card.
But four tries after the break — including Matai Leuta demonstrating his excellent balance as he sprinted for the whitewash along the touchline — sent them through.
Earlier, the USA defeated Japan (52-0) and beat Spain (38-17) to set up tomorrow’s clash with England.
Fiji survived a late scare against England in the final Pool C match of the day to ensure they finished top.
They were two converted tries clear with just over a minute to play when Will Muir attacked the right-hand wing to dot down before Alex Davis did the same down the opposite side. Muir’s try went unconverted and Fiji stole the ball from the restart in a thrilling climax.
Fiji had earlier run rampant against France (50-0) and Kenya (38-7) on an impressive opening day.
England were made to work for victory over Kenya, who came back from an early deficit to take a brief lead, but Dan Norton’s hat-trick completed a 29-12 victory. France’s Nisie Huyard scored two tries but it wasn’t enough to prevent defeat against England (26-12).
Australia once again picked up three wins on the opening day, with a Maurice Longbottom try in the final seconds against Wales got them off to a good start.
John Porch ended the day with four tries including a hat-trick against Canada as his Australian team also dispatched with Scotland.
The Scots put four tries past Wales (28-7) after their own last-ditch victory against Canada.
Longbottom gave Australia a first and fourth minute try with Jesse Parahi scoring in between times. Tries from Robbie Fergusson and Harvey Elms got Scotland onto the scoreboard but they never looked like coming back, and had to settle for second place.
Justin Douglas became Canada’s all-time leading try scorer in the HSBC World Rugby Sevens Series, but his side could only manage victory over Wales as they had to settle for third.
He scored two tries in their defeat to Scotland to draw him level with Sean Duke, before a second-minute try against Wales took him onto 125 and above his countryman. Douglas added a further try to his tally to help secure victory.