In her 2017 book, "Thinking About Child Abuse,” Haru Sugiyama describes her correspondence with Yukihiro Saito, who is serving a lengthy sentence for causing the death of his 5-year-old son, Riku, in the mid-2000s through neglect. In his letters, Saito expresses regret, but also says his memories about the two years he took care of Riku after his wife left him are vague.