The Koreans had the better of the chances at the Jiangning Sports Centre, with Ri Un-sim hitting a post and Kim So-hyang miscuing in front of an open goal.
But Japan snatched victory seconds before the final whistle as Norimatsu met a right-wing corner to score.
These two teams are strongly fancied to fill two of the top three places in the six-team round-robin tournament which earn spots at next year’s FIFA U-17 Women’s World Cup, but Japan are now firmly in the box seat at this early stage.
DPR Korea were the first to threaten and a Ri Hyang-sim’s cross from the right broke to Kim Phyong-Hwa, but her shot was charged down.
At the other end, Japan captain Yui Narumiya raced down the left and fired in a low cross which was scrambled clear at the near post.
Fireworks started going off outside the stadium midway through the half, but both sides were struggling to spark on the pitch.
Choe Hyang-mi blazed over the bar when the ball dropped to her unmarked on the edge of the area before Ri Un-sim went desperately close in the dying minutes of the first half.
The striker’s shot from just outside the area was powerful and had goalkeeper Risa Shimizu beaten, but cannoned back off the left-hand post.
DPR Korea were in the ascendancy and Kim So-hyang had a golden chance soon after the break.
Shimizu failed to claim the ball and presented her with an open goal, but with the ball bouncing she missed her kick at the vital moment.
Kim Phyong-Hwa headed straight at Shimizu as Hwang Yong-bong’s side continued to look the most likely scorers, but they were almost undone from a corner.
The delivery from the right picked out Sumida unmarked in the middle six yards out, but she could only direct her header straight at keeper Rim Yong-hwa.
Japan were still struggling to carve out chances from open play, though, and Sasaki let her frustrations show with a late tackle on Choe which earned her a yellow card.
But Hiroshi Yoshida’s team were celebrating soon after following just about the last action of the game.
Norimatsu met a right-wing corner with a perfect header which gave Rim no chance.