This story is about an Anon who goes around looking for yukkuri nests, but only approaching the ones that have a lot of yukkuris. There, he bribes them to bring their food out, then challenges them to a game.
If they guess which cup the stone is under, they get 1 sweet. Lose, they give an equivalent. Gradually they win the first few rounds, and the stakes go up. After a sudden rise from 6 sweets to 20, the yukkuri lose. Naturally the Reimu accuses him of cheating, but he points out that they chose wrongly, and there's a 50% of getting it right. After a bit more reminding of what they promised (Reimu said she understood what he was asking whenever he asked for confirmation), they give in and pay up, losing all of their food...
The Marisa mate scolds Reimu for giving away the food, but Reimu remains stubborn. Anon asks why they had so many children (around 20) when winter was near, and Reimu replies that Marisa had a lot of food, etc. That's when the guy realizes it's a Deibu, doing what it likes.
The family still owe the equivalent of two sweets, so Anon persuades them to put the children up as collateral (one ko for two sweets), promising not to kill them. Marisa goes into the nest and realizes that ALL the collected food is gone, and Anon explains the details to her. The parents argue, until a ko tells them to stop. At Anon's suggestion, Marisa goes off to hunt so that they can buy their ko back.
While Marisa's gone, he informs Reimu that she could put more children up as collateral and bet again, reminding her that she won quite a few rounds in the beginning. After some thought, Reimu agrees. She wins that round and gets her child back, but chooses to play some more. Marisa's existence diminishes as she easily gained what Marisa worked so hard to get.
She wins the next four rounds, retrieving the food and getting 30 sweets. Finally, he proposes a bet of 90, telling them they can probably make it through winter with all that sweets. As he's slipping the stone into the cup, he points behind the yukkuri, saying there was one large sweet that vanished. They're fooled, and don't see that he switched the stone around.
After one last reminder of what's at stake, the game starts. Of course Reimu loses. Food + what Marisa came back with = 9 sweets The 30 sweets Reimu won. 25 kos X 2 = 50 sweets. She's still short of 1 more. He reminds her she still has kos... on her stalk.
He now tells her a new exchange plan, 10 sweets for one ko's life, with the 4 on each of the 3 stalks she has, that would make 120. When he makes to leave, Reimu chooses to play.
He moves quickly, flashing one cup at her to show her its empty as a service, before asking her to pick. She picks the other one... but it's not there. Due to the speed, the stone is lodged in the one he flashed at her. She accuses him of cheating, but he points out that showing her didn't mean it wasn't inside.
Then he starts eating the kos, all 12 of them. After he's done, he tells Reimu she can just refresh to make some more. Then he offers her one final bet... herself, at the price of 100 sweets. Of course, betting is about risking your life...
Marisa returns from hunting, and there stands Reimu.