Husband-and-wife vocal duo Humbert Humbert sing the theme song of the NHK serial morning drama “Bakebake” (“The Ghost Writer’s Wife”). The song’s title, “Warattari Korondari,” means “laughing and tumbling.” Yuho Sano, wife, and Ryosei Sato, husband — whose cheerful voices greet viewers every morning — spoke recently with The Yomiuri Shimbun about their everyday lives and what music means to them.