This is not a pyroclastic flow, it is the collapse of a phreatic eruption column. The highest temperature should be close to the boiling point of water at that altitude.
They are confused, not understanding that an eruption has occurred. They say, "Let's go to the shelter. Cover your mouth." They are having a conversation.
I climbed this Ontake twice in Fall and a winter, but it was peaceful that time 10% of the world active volcano is in Japan, and take caution. I also went Aso in Kyushu last year, and now it erupted, that is living in Japan