Summary by platina:
A Reimu, assisted by a human caretaker, opens a day care center for wild yukkuris in a prefab shed in the forest. Reimu is a good teacher and the little ones love her, but she's awaiting the day when this is all over and she can be reunited with her own little ones. The caretaker shows her DVD footage of her little ones.
Reimu teaches the little ones a song and dance routine for a special recital where they'll perform for the school founder, a man who loves yukkuris. The little ones practice hard and help each other get better. The parent yukkuris are invited to to recital day and told that free sweet-sweets will be distributed to everyone.
Presentation day. The parent yukkuris are shown to the audience seats behind a large sheet of plastic, ostensibly to keep the little ones from falling off the stage and getting hurt. The founder arrives and is seated in a place of honor. Reimu leads the little one in the song and dance they've worked so hard to learn, and the parents are delighted by the performance.
However, the founder says they suck, he can't take it easy at all. To punish them for performing badly, the caretaker starts flicking them in the forehead, then sticking them with pins or burning them with a lighter, and then finally, getting tired of doing it individually, spraying them with yukkuricide (not enough to kill them, just enough to make them suffer). Then the founder hands the caretaker another spray bottle, and he sprays them all with orange juice, healing them and cheering them up again. The parents, initially horrified, soon put the bad thoughts out of their head--after all, nobody died, and the humans gave the little ones sweet-sweets, and coming up next is lunchtime.
However, the caretaker brings not lunch, but a big piece of sheet metal. The founder has Reimu line the little ones up in a square as they had practiced, then he puts the metal on top of them. The little ones aren't crushed, but they're immobilized.
The parents start asking the founder to stop it, the little ones can't take it easy. The founder laughs that they still don't get it, he set up the daycare center and everything just to abuse them. He says Reimu has been working for him all along. The little ones beg her to say it's not true. The founder reminds Reimu that her little ones are waiting for her in his car, and she tells all the wild yukkuris that she hates them, that she did all this for her children and the rest of them can die.
Reimu was a stray, struggling to support her two children. She was caught trying to take flowers from the founder's garden, and got roped into this deal. Having already faced near-certain death, she was resolved to do anything for her children. As a street-toughened stray, at first she was contemptuous of the pure, innocent forest yukkuris, but in teaching the little ones every day, she grew to care for them. But with her children held hostage, there was nothing she could do. The little wild yukkuris would probably die, so she might as well make them and the parents hate her now.
Saying it's something he always wanted to do, the founder jumps and lands on the metal sheet.
There is a massive squelch.
He lifts the sheet, showing the underside to the parents. They fall into a frenzy of horror and rage and sorrow. The founder muses that next time, he should use a transparent sheet instead of a metal one.
The humans prepare to take their leave. The caretaker takes down the video cameras that have been recording all this. The founder tells him to finish off the parents--they could tell people what he did and cause trouble--but first, he brings Reimu's little ones in from the car and releases them among the parents, where they are tormented and crushed to death in revenge. Reimu accuses the humans of breaking their promise, but the caretaker says "So?" and tosses her to the parents as well. The parents kill Reimu, never considering that the humans are ultimately to blame, and eventually, they, too, are killed by the caretaker.
On the way home, the founder is listening the the news on the radio. He hears about a daycare-center manager sentenced to 20 years for child-molestation, and a mad killer who said his motive was just to kill someone--anyone. The founder, disgusted, says both of them should get the death penalty--they must be sick in the head, harming people when they could just kill yukkuris.