This is the third story in あさつき堂合同誌寄稿総集編Dark (Asatsuki Dou Compilation from Collaborated Anthologies - DARK". There're 3 stories in this book:

An Excerpt of a Certain Children's Folk Song Passed Down in the Human Village
Killing Me, Killing You (prequel to Miniature Garden)
Miniature Garden (sequel to Killing Me, Killing You)