The Kokori Children vanished after the Deku tree was destroyed in a war long ago. Their village has decayed through the years, but their spirits still haunt the ruins, playing childish tricks on those who wander through.
In the shadows of the remains of the central building is a staircase leading to a tunnel woven into the roots of the village. However, it is blocked off by thorny vines. Upon investigating it, the ghost of a child appears. "I was playing hide and seek, but I couldn't find anyone. I've been looking... for a long time. Will you help me?" This will prompt other ghosts to appear in other houses.
In the other ruined houses, Link can find the other ghost children hiding under boxes or behind bookshelves. As Link approaches, he can hear the ghost giggling. When he moves the box or bookshelf, the ghost will appear and circle around him, saying "Can't catch me!".
Link has to hit the ghost with his boomerang to still it, upon which it will say something. "The Deku Tree told us to play hide and seek a while ago. Have you been looking this whole time?" "You aren't as scary as the other people who were looking for us." "I didn't know if anyone would be able to find us! Who told us to hide again? Is he still here?" The implication being that the Deku Tree saw the war coming and when Ganondorf's troops showed up to destroy the tree, it told the children to hide so they wouldn't be killed. And they've been hiding ever since, even though the Deku Tree was uprooted and the children became ghosts. (If we're feeling fairly dark, we could have little piles of bones under the boxes or whatever, as if the children died waiting to be found.)(That's pretty dark though.)
After finding three ghost children, Link goes back to the central building and can talk to the first ghost. "The Deku Tree told me I was it because I was the strongest. My friends were hiding for a long time. But I don't know if anyone won the game..." The ghost fades away and the thorns disappear, allowing Link to access the staircase.
Link can go down to the tunnel, which has some enemies and a puzzle or two. At the end is the Acrobat Talisman (or if we don't decide to use the magic talismans, some other reward).