@burcinc, @turkay1-- No one said that KAATSU is without risks. But I think that it's a safe method if you do it right. The important part is to start out easy, doing a few sets and then slowly building that up over the course of weeks.
Plus, KAATSU doesn't want to stop blood flow all together. The point is to decrease blood flow, so the belts should not be extremely tight and they are only supposed to stay on for a maximum of ten minutes. If you loose numbness or your skin looks very pale, you're supposed to stop immediately.
I think if these points are followed, KAATSU is safe and it gives great results. It's safer than some high intensity training options in my view.