Yamagata in February. The winter was approaching the end in the flatland. I was aiming for the summit of Mt. Zao for the night. There is a crater lake which is still active as a volcano called Goshiki-numa, and in the summer it is a beautiful lake of emerald green. It was covered with strong wind and fog, but it showed its appearance in a moment of fine weather. The crater lake where the accumulated snow began to melt was like a blue moon.