Shinju (from the Japanese 真珠 meaning pearl) is a word used euphemistically in Japanese of the female breast. It is also popularly used as the name of a type of female halter top in the clothing industry.
It has been popularly claimed that "shinju" is an authentic Japanese term for a breast bondage tie. The tie is usually shown to be something similar to what in the west bondage is called a "bikini harness". See Illustrated Tie  There is however, no such tie called a "shinju" found in historic or present "Kinbaku" (Japanese Bondage). The word was erroneously applied to Japanese Rope Bondage in Europe in the mid-1990s by commercial websites.
The basic or foundational Kinbaku form of binding the arms and breasts is known as the "Ushiro Takatekote"; which is to bind the arms behind (ushiro) the back in a box arm position (takate kote). This basic box arm tie originally found in the samurai martial art of Hojōjutsu (捕縄術) or Nawajutsu, (縄術) evolved into its erotic usage at the end of the 19th century and early 20th century, and is foundational to most other Kinbaku ties.
- Shibari You Can Use, Lee Harrington, ISBN 978-0-6151-4490-0: Pages 51-96