Responses
Red thread is usually a thread of fate. Black thread might be to do with bad luck. Bottom got bad luck after he got attached to the thread. top says he comes from shamans so he probably connected their strings accidentally while being jealous of bottom getting lead role. He gave his bad luck to the bottom. That’s my theory but red is almost always string of fate. Whether they like it or not, they were destined to be connected.

Why does it feel like the seme knows about the thread?and why does his thread is black but in the uke it's red?it looks like he knows why it suddenly came out