The City forward carried on her rich vein of scoring form at this summer’s tournament with her third strike in two matches, latching on to Lucy Bronze’s floated cross with 15 to play.
White’s decisive contribution bucked the trend of a generally cagey affair, with neither side able to gain a stranglehold on proceedings in Sapporo.
Seven City stars were given the nod to start by Hege Riise, with Ellie Roebuck’s goal shielded by Bronze, Steph Houghton and Demi Stokes, while Keira Walsh started in a midfield three.
White and Lauren Hemp started as part of the front three alongside former City star Nikita Parris but, despite the quality on show, neither side were able to break the deadlock in a first half of few talking points.
Indeed, it was the hosts who perhaps carved out the best chance of the opening 45 with Mina Tanaka flashing an effort just wide of Roebuck’s far post following a swift counter.
However, Team GB were unphased by that opportunity, with Walsh combining effectively with Arsenal’s Kim Little and Chelsea’s Sophie Ingle to keep things ticking over and snuff out any real Japanese danger in the heart of midfield.
The stalemate continued after the restart, with Stokes and Hemp locked in an intriguing battle with Japan right back Risa Shimitzu, as they too looked to spark a cautious affair into life.
In need of inspiration, Caroline Weir entered the fray just before the hour, replacing Ingle to sit alongside Walsh and Little and link play.
The change brought a new-found positivity, as Hege Riise’s side slowly began to gain a foothold in the game.
Chances came and went, with Houghton’s instinctive volley from a corner flashing over the bar before Parris’ cleverly disguised effort from the right fell inches wide of the far post.
But Great Britain’s ascendancy was finally rewarded in the 74th minute with the game’s deciding goal as White, gambling with a clever near-post run, beat the onrushing Ayaka Yamashita to Bronze’s teasing ball in and glanced home the winner.
It was just rewards for the City forward who had struggled to make her mark on the match up to that point despite her tireless efforts in leading the line.
City duo Georgia Stanway and Jill Scott were brought on in the 87th minute to help see home the three points, replacing Hemp and Little, but there was still time for Weir to almost double Great Britain’s advantage.
The Scottish midfielder curled a sumptuous free-kick from the left over the wall, but couldn’t quite get enough dip on the effort to trouble Yamashita’s net as the game approached stoppage time.
Nonetheless, Team GB held on to earn a crucial victory and secure their progression from Group E ahead of a difficult encounter against Janine Beckie’s Canada on Tuesday 27 July.
Hege Riise’s side currently sit top of the group going into their final match, with six points from their two matches, while Canada are one place and two points worse off.
Host nation Japan are third with one point, meaning victory over fourth-placed Chile and a Canada defeat against Team GB could see them into the knockout stages.
