Hyakuta's wrote a book called Jun'ai (2014) in memory of his recently deceased friend, the radio and TV show host Yashiki Takajin. The book, written as if it were a work of reporting, portrayed Takajin's daughter and his manager as callous, cruel individuals who abandoned him in his final days. Takajin's manager and daughter both sued for slander. Hyakuta claimed that although all the persons named were real, the book was "fiction." He had relied heavily on uncritical interviews with Takajin's widow, and did not mention her bigamy in the text of the book, only admitting to it later. After multiple appeals, in December 2017 the Supreme Court of Japan found that Hyakuta had slandered Takajin's daughter and ordered 3.65 million yen paid in compensation. In November 2018 the Tokyo District Court found that Hyakuta had slandered Takajin's manager as well, ordering an additional 2.75 million yen in compensation and a written apology.