The Koreans showed some deft passing skills but didn't have a shot at goal until early in the second quarter from Kim Ji Eun although the ball sailed way above the head of goalkeeper Sally Rutherford.
However, the hosts kept applying consistent pressure to force the Koreans into making errors to concede possession.
From one such passage of play Merry latched on to the ball, slipped into the D before unselfishly flicking it to an unmarked Sophie Cocks to make it 2-0.
Even before the scorers gave their fingers a rest from the electronic keyboard, they were furiously typing in 3-0 after Anita Punt gave a glimpse of what the New Zealanders are capable of from penalty corners in the 21st minute.
In the earlier quarterfinals on day four of the HB Festival of Hockey today, Japan beat India 3-1, China made hard work of it before pipping non-Olympic qualifiers Canada 1-0 while the Australians eventually ground down the other non-Olympic side, Ireland, 3-0.
Early in the second half there were a couple of "ohh!" moments after striker Rachel McCann came close to making it 4-0 but lost control from point-blank range with the keeper grounded.
Coach Mark Hager won't mince words when he reviews the videotape with the women tomorrow after another couple of sitters went begging amid poor option taking under pressure in the D for a goalless third quarter.
However, while all the focus is on the coalface some kudos should be heaped on the Black Sticks' defence of Julia King, Emily Gaddum, Kirsten Pearce and Liz Thompson which thwarted Korea's well-laid attacks time and again.
It was 4-0 two minutes into the final quarter when captain Stacey Michelsen showed some individual brilliance to worm her way through the traffic jam to slot the ball into the backboard.
Punt collected her second, making it 5-0 from a penalty corner in the penultimate minute but what compounded Korea's problems was the sinbinning of a defender before the goal was taken.
But the Sticks weren't done. Merry put the visitors out of their misery, 6-0, just before the hooter in what will probably be her easiest pickings when she simply tapped in a ball at the far post after the keeper made a total hash of a Pippa Hayward flick.
Officially, though, the website appears to credit the fifth goal to Hayward.