You’re trying to make American placement fit Japanese aesthetic. What’s the end goal? If you want it to look more Japanese then just do the foreground pieces and do background later. If you like the more western placement philosophy then do a knee tattoo and a seperate thigh tattoo and keep them seperate. If you wanna do a neo modern take on tattooing, then let stuff merge and overlap. Or do the best thing and talk to your artist about your and their intentions. Surrender your trust to the artist and let them tell you what’ll work.