SHORT ANSWER: YES

Anyone who intends to manufacture or import more than 1 ton of phase-in substance and more than 0.1 ton of non-phase-in substance has to comply the K-REACH. So anyone who wants to export phase-in-substance (more than 1t/y) or non-phase-in-substance (more than 0.1t/y) to Korea, they have to register their substances indirectly through their importer.