Two people, two ropes, apparently linked. The loops that could be linked run through the bodies — and their linking number is zero. The wrist gap is the doorway.
Each rope looks like a closed ring, so the pair looks like two links of a chain. But neither rope is closed: each one is just a segment, and its "loop" is completed through a human body — up one arm, across the chest, down the other arm. The curves that could actually be linked are those rope-plus-body loops.
And a body-loop comes with a built-in doorway: the tie at each wrist is a loose cuff, and there is a gap between the cuff and the skin. Feed a fold of the other rope through that gap, slide it over the hand, and the "links" simply come apart — no untying, no cutting.