The spectacle, filmed around 7 a.m., showcased Japan’s largest caldera lake completely veiled in a blanket of white.
This phenomenon occurred as the morning chill cooled the air above the water surface, causing water vapor to condense into a thick layer of cloud that hovered low over the lake.
September 23rd marked the autumn equinox, the midpoint of the season when day and night are nearly equal in length.
The view of the lake shrouded in mist created a dreamlike scene that seemed to herald the footsteps of winter.
https://newsonjapan.com/article/147013.php