ISESAKI, Japan — Hideo Yokoyama is one of Japan’s most popular crime novelists. Yet he regards the crime as the least interesting part of the stories he tells.

“Usually, in a mystery or thriller, the main character is the detective, and the crime is the main ingredient,” said Mr. Yokoyama during an interview in the home he shares with his wife, Fumie, in a quiet residential neighborhood about 75 miles northwest of central Tokyo. “But is that really a special thing for the detective? It’s not a big deal for the detective.”

Instead, Mr. Yokoyama, 60, speaking through an interpreter, said he is interested in the psychology and social dynamics of characters who happen to be affected by crime. In the case of “Six Four,” his 15th novel and the first to be translated into English, the main character, Yoshinobu Mikami, is not a detective but a police department spokesman ensnared in a 14-year-old unsolved kidnapping case while his own teenage daughter has gone missing.

While there is a whodunit aspect to the novel (and a spectacular twist at the end), much of the book’s 560-plus pages are devoted to probing Mikami’s domestic life with his wife, a former detective, as they navigate their marriage after their daughter runs away, and exploring the treacherous police bureaucracy and its combative relations with the news media.