“This is my wife, Miku,” the 39-year-old school clerk said, showing a life-size Miku doll sitting on a folding chair with her signature long turquoise pigtails almost reaching the floor.

CHIBA--Hatsune Miku has always been 16 years old and worn long aqua ponytails. She is Japan’s most famous Vocaloid--a computer-synthesized singing voice software that, in her case, comes with a ...