19。

The protagonist, Mayama, one day notices a mysterious thread wrapped around his hand. This thread sometimes violently binds his palm, causing pain, and it never disappears. Before long, Mayama finds himself surrounded by his homeroom teacher, his faceless father, and classmates entangled in threads. And then there's the childhood trauma related to the thread… To unravel the mystery of the thread, Mayama begins to touch people's hearts.