Loose socks (Japanese: ルーズソックス, rūzu sokkusu) are a type of sock that is popular among Japanese high school girls. They originated from boot socks for mountain climbing, manufactured in and exported from the United States. They usually white but black and navy are seen.
In Japan, they were adopted as a fashion that deviated from school uniforms and firmly took root after a long period of popularity.
They were first worn by high school girls and later by junior high school girls, but not other ages. The fashion is so unpopular with other age groups that it is said that loose socks equal high school girls. Since the socks are worn to go with school uniforms, they generally haven't come into fashion with elementary school students. There are also virtually no girls who keep wearing loose socks after they graduate from high school. Those who do tend to be viewed as strange.