Do kinoki foot pads really remove toxins and heavy metals from the body? If so, how?

No, they don’t. It’s a 100% scam.

My partner bought some to test them. He wore one set on his feet and left two other sets unwrapped and exposed overnight. In the morning, all of the sets looked the same. They do go from white unwrapped to muddy-looking unwrapped after several hours, but the process is almost certainly oxidation-based and nothing that removes toxins—obviously, not anything associated with being in the proximity of a body. They also smell funky.