This is a way of adding box-tie style arm support at the end of a Shinju, or generally to most any chest harness. You need to tie it with a fair bit of tension in order for it to be effective, but you don't want to use it as a main load-bearing element during suspension; at most it should take maybe 10-20% of the load on the chest harness.

I first saw this method demonstrated by Trialsinner at the first Boston GRUE sometime around 2010 or 2011; in fact I think he may have come up with it on the spot during our working session on chest-loading suspension harnesses. I specifically remember using it in this 2011 photo of Mecha-Kate:

Trialsinner has a photo of the technique used with a non-Shinju chest harness that he developed here.

This all predated my discovery of the Chest Loading Takate Kote family of methods, which I rapidly came to prefer for what I was seeking at the time; but in recently revisiting the Reverse Kannuki method, I've come to feel it has a niche where it works well -- mostly when you want the restriction of a box tie but the simplicity and safety of a Shinju-based suspension. That said, it seems to be somewhat a matter of taste; some bottoms like it, others hate it.