It is a migratory butterfly called chestnut tiger.
He seems to like a flower called Fujibakama, and I often see him perching on this flower.

chestnut tiger seems to be in the cool highland area of Honshu from spring to summer, but in autumn it seems to fly to Kyushu and further south in search of a place to live at the right temperature.

Fujibakama is one of the seven autumn herbs and is also a seasonal word for autumn.

At a glance, I thought, "It's autumn in Japan! I don't think it's a photo, but it's actually a unique combination of autumn.