It would be hard to find Japanese young girl (I would say in the 20th of age) who have natural black hair. To dye black hair lighter has become common in young girl for10 to 20 decades, and even having black hair is thought it’s behind a trend.
But when those girls go to a job interview, they dye the lighter hair to black as having a job interview with lighter hair could be inappropriate. Or some just dye light hair dark on the day, temporary. Isn’t it funny?
However actually many men think that an ideal girl who they want to get married with is having black hair as having black hair is seen as a honest person.