Yuki is a lovely Japanese girl who's good at origami. When Dora traveled to Tokyo, she met Yuki at a nearby building. They became friends and Yuki taught Dora the art of origami. She taught her how to make boats, planes, swans, and other creatures. Dora tells Benny and Boots that in "Benny's Treasure".
Yuki appears in the episode "Benny's Treasure," even in the flashback part.