Australia U20s delivered a second-half masterclass to win 54-27 over Eddie Jones's Japan U23 in Coffs Harbour.
Replacement half James Martens was the standout, crossing for a double and setting up another as the Aussies ran away with the game.
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Winger Cooper Watters and replacement Eli Langi also impressed, as coach Chris Whitaker starts his tenure on a high.
The opening half was a battle of styles as it was Japan's pack that sought to counter Australia's explosive outside backs.
Hooker Kenshin Shimizu crossed for a hat-trick of tries via the rolling maul for the Japanese side as they dominated up-front early.
Xavier Rubins's fourth-minute try kept Australia in it, and fullback Shane Wilcox crossed in the 26th to leave the hosts down 19-14 at halftime.
Watters levelled the scores after nice interchange with centre Liam Grover put him into space.
With unlimited substitues allowed, Martens came into the number nine jersey and caused havoc.
It started at the 47th minute when the Reds half backed up Langi's break from the ruck to dive over.
Martens then showed his smarts to catch Japan napping with a quick tap, handing off for Beau Morrison for the five pointer.
He then crossed for his second to go Australia a comprehensive lead, leaving Jones disappointed on the sidelines.
The former Wallabies coach's mood was soured when Langi charged down the kick and sprinted away to extend the advantage.
Japan crossed late but the night was Australia's and Joey Fowler sealed the win and the half-century.
Australia U20s 54 (Martens 2, Fowler, Morrison, Langi, Watters, Wilcox, Rubins tries; Cons: Dillon 3, Prass 3, Fowler) def Japan U23s 26 (Shimizu 3, Isobe tries; Cons: Taira 3)
