What Does This Positive Cable Lead To?

The two cyan circles are both ends of one cable, the yellow circle is the starter, and the black is negative, I've tried looking through my Haynes manual for the electrics diagram but it says the yellow should go to a stater relay but I cant see one and I cant see where the other end of the positive goes. does it go to the ecu? There's a small red cable that goes to the fuse box, but I'm really struggling, any info would be greatly appreciated