This file photo shows the hot spring resort town of Kusatsu in Gunma Prefecture bustling ... and some hotels to regulate late-night in-room baths to allow water levels to recover gradually.

KUSATSU, Gunma Prefecture--A 13-meter-tall tree set in front of the Kusatsu onsen’s iconic “Yubatake” (hot spring field) here is being extravagantly illuminated each night with about 33,000 ...