Fruean and New Zealand's first try came after four minutes, then the number 13 crashed through the Welsh midfield six minutes to claim his second and his hat-trick score came in the 13th-minute when he touched down after fielding a cross-field kick from Renata.
17-0 down, Wales came back into the game when their winger Jimmy Norris narrowly missed out on scoring and the Baby Blacks' try-scoring hero Fruean was then sin-binned for committing a professional foul in the 24th-minute. A loose ball from Renata was pounced upon by Wales number 10 Gareth Owen and he raced over under the posts for his side's first try, which winger Leigh Halfpenny converted.
A Renata penalty handed New Zealand a 20-7 half-time lead and despite a poor start to the second period, the Baby Blacks went 25-7 ahead when flying winger Kade Poki finished off a superb team try in the left corner.
Wales loosehead prop Ryan Bevington raised his side's hopes of a comeback when he charged over, showing a good turn of pace to evade the retreating Kiwi players and Halfpenny's excellent conversion reducing the arrears to 25-14.
But Keiron Crowley's men seemed to have another gear and a 57th-minute try from inside centre Ryan Crotty, who was teed up beautifully by replacement number 10 Daniel Kirkpatrick, sent them further ahead.
They wrapped up the win on 69 minutes when another replacement Luke Braid touched down, after he fielded an excellent cross-field kick from Kirkpatrick.
Argentina, meanwhile, proved too strong for Japan at Shaw's Bridge in a 41-8 win. An unconverted try from centre Yasutaka Sasakura, who was put away by scrum half Tappei Higashide, had the Japanese right in contention at the break as they trailed by 10-5.
But the Argentinians raced clear in the second half thanks to tries from winger Ignacio Poet Belmonte, captain and full-back Belisario Agulla, scrum half Martin Landajo, centre Juan Pablo Socino and replacement winger Manuel Trebucq.
England fought back to defeat Samoa 20-12 at Shaw's Bridge to claim their first points of the tournament. The Samoans looked well placed as they led 9-3 courtesy of three penalties from the boot of full-back Titi Jnr Esau after 10, 18 and 25 minutes. They also had a numerical advantage when England lost Northampton winger David Smith to a 22nd-minute sin-binning.
Nonetheless, England crucially had the better of the closing minutes of the first half when they struck for 10 points in a 10-minute period. Out-half Adam Greendale created the opening for England's first try, breaking clear of the defence before he was halted a metre from the try-line, and captain and number eight Hugo Ellis was one of the players to follow up and he dotted down for his sixth try in his last three internationals.
Full-back Alex Goode, who had earlier kicked a penalty, landed the conversion and tagged on his second penalty just before the half-time whistle.
Ellis' Wasps colleague Joe Simpson scored what was effectively the match-winning try, fifteen minutes from the end. The lively scrum half took the ball on off the back of a ruck and powered over past two tacklers with Goode adding the extras.
Ravenhill's second game tonight ended in disappointment for hosts Ireland as they saw a 5-0 half-time advantage - Blackrock winger Niall Morris bagged a 14th-minute - overturned as the 14 men of Australia showed plenty of resolve by coming from behind for a 15-10 victory. The Aussies had their number eight Michael Uoka sent off just before half-time for swinging his arm dangerously at a ruck.
But two tries from elusive winger Andrew Barrett and a late penalty from centre Rowan Kellam were enough to see the defending champions chalk up win number one in this year's tournament. Replacement hooker Michael Sherry notched a second half try to take Ireland's tally to 10 points.
Elsewhere, the two matches held at Belfast Harlequins' Deramore Park ground this evening resulted in wins for South Africa (36-5 against Fiji) and France (11-6 against Scotland). The South Africans looked a totally different side to the one that finished a disappointing eighth at the 2006 tournament in Dubai as prop Corne Fourie, flanker Johan van Deventer, full-back Wilton Pietersen (2) and centre Stefan Watermeyer (2) ran in tries against the Fijians.
However, there was one moment for Fiji and their fans to savour as just before the interval, flanker Jese Cirikisuva crossed to score their only points of the match, but there was added significance to the score as it marked their first ever points in Division A.
The French, led by experienced out-half Morgan Parra, erased a 6-3 deficit against Scotland with number eight Raphael Lakafia grabbing the clinching try in the 67th-minute. Centre Stephen McColl kicked two penalties for the Scots.
IRB U-19 WORLD CHAMPIONSHIP - DIVISION A DAY ONE RESULTS:
South Africa 36 Fiji 5, Belfast Harlequins
New Zealand 37 Wales 14, Ravenhill
Argentina 41 Japan 8, Shaw's Bridge
Samoa 12 England 20, Shaw's Bridge
Australia 15 Ireland 10, Ravenhill
Scotland 6 France 11, Belfast Harlequins
DIVISION B NEXT FIXTURES:
- Monday, April 9 -
South Africa v France, Ravenhill, 5.30pm
New Zealand v Japan, Belfast Harlequins, 5.30pm
Samoa v Wales, Shaw's Bridge, 5.30pm
Argentina v England, Belfast Harlequins, 7.30pm
Scotland v Ireland, Ravenhill, 7.30pm
Australia v Fiji, Shaw's Bridge, 7.30pm