Great Britain had mixed starts to the Visa International Invitational Hockey Tournament at Olympic Park, with the women beating Korea and the men losing to Germany.
Reading forward Alex Danson marked a half-century of GB caps with the only goal - her 50th at international level - eight minutes from time.
Her reverse-stick effort from the left of the circle looped up off the glove of goalkeeper Younghui Moon and into the far side of the net.
"I'm not overly disappointed with our performance, we got a win, but I am disappointed that we didn't take the good chances we had," said coach Danny Kerry, whose captain Kate Walsh made her 100th GB appearance.
Reigning world champions Argentina lead the standings after a 3-0 win over China.
Great Britain's men controversially went behind to a Florian Fuchs goal seconds after the interval while some of their players were still returning to the pitch after the break.
Christophe Zeller and Moritz Furste increased Germany's lead before Ashley Jackson pulled one back from the penalty spot to make the final score 3-1.
"The result's a little disappointing but there's plenty to be optimistic about," said coach Jason Lee.
GB's women face China on Thursday while the men take on India, who lost 3-0 to Australia.