I found these in the children's fiction section of Tsutaya in Shibuya, shelved somewhere between Winnie the Pooh and the Moomins. It's a small section, just four or five shelves, and so each book is presumably chosen with some care. This begs the question: are these normal children's books, or am I ultra prudish?
Literally, the title of this book in English is 'Shit!' Or so says Google translate.