Koji Kosen

Koji Kosen is a mineral spring in Japan whose waters fall within the kosen category, a classification used for naturally carbonated or acidic spring waters that do not meet the higher mineral concentration thresholds of full hot spring qualification but are nonetheless valued for their distinctive character within the bathing tradition. The kosen designation acknowledges that many of Japan's most historically valued mineral spring sites produce waters of distinctive character even when their total dissolved mineral content falls below the standard hot spring threshold, preserving the cultural importance of these springs within the broader landscape of Japanese balneological tradition. The spring provides a gentle and refreshing bathing experience appropriate for visitors of all ages, representing the diverse spectrum of Japanese mineral spring culture that extends well beyond the most famous sulfurous and highly mineralized volcanic sources.