Do NOT tag this Justice. The whole story is basically Anon driving the yukkuris into madness in order to troll them.
Anon picks up a family that had just gotten kids, separating the parents on the reason that they're 'sick'. He gives them one 'pill' to divide between both of them, but the Reimu takes it all. The Marisa gets angry at being the only one to die, and they start arguing. When the children try to stop their parents from fighting, Reimu kills them for siding with Marisa. Anon kills Marisa with a chainsaw to 'prevent the spread of disease', but later kills Reimu as well, saying that he can't let such a bad parent go free. In truth, he simply likes to abuse yukkuris with unreasonable reasons and watch them scream because of it.