Japan’s foreign residents have surged to a record 3.77 million by end-2024, with over 2.3 million foreign workers by October, fueling debate on immigration and aging. The author, who specializes in senior employment support, asks what happens when these workers eventually age in Japan: while some may qualify for permanent residency via specific skilled visa tracks, many will not stay indefinitely, possibly returning home or continuing to work into older ages. Careful planning is needed for their aging: language and cultural barriers in facilities, rising costs, and staff shortages threaten services. If Japan intends to keep many foreign workers long-term, eldercare design and social insurance systems must be prepared to include them.