This is a rather mysterious haiku. I did the English translation, but I am not sure if I got it right. It seems the haijin looked one spring day at the sky. He might have felt that the particular color of the eternal sky seemed to suggest that everything ended there.
I remember I took up this haiku and made haiga from it when there was a big news of a space shuttle exploding in midair. The shuttle broke in to pieces and melted in the blue of the sky.