Since birth, Kaoru Kamisawa has had the ability to see the "threads that connect people," supernatural strings that represent relationships of romantic, platonic, and adversarial in nature. In addition, he can cut these strands, allowing him to sever connections. However, Kaoru has no red thread—the string of soulmates—of his own, leading him to seek a life without meaningful relationships.

But this all changed when he met Hara Kazunori, a man who pursued Kaoru despite lacking a red string. Kaoru’s reticence soon gave way, and the two started dating. Their romantic bliss, however, is not fated to last. One day, Kaoru sees that a red string has appeared on Hara's finger—and it is not connected to him.

[Written by MAL Rewrite]