The Japanese believe in the red thread of fate. This originated from Chinese myths of a deity who would tie couples together. According to the myth, destined lovers will be tied by the red thread forever, regardless of time and circumstances. It may tangle and it may stretch but it will never break.

The red thread of fate is so ingrained in Japanese culture it has shown up in various places. In the Negima OVA, Negi casts a spell which ties him and Nodoka together with a red string, which cannot be broken even by Asuna’s anti-magic fan/sword. In Pokemon Diamond and Pearl, there is a item to be held by Pokemon called the Destiny Knot. When the Pokemon holding the item is infatuated, so is the opposing Pokemon.