A proverb likening a man's heart to the changeable autumn sky, meaning men's feelings are fickle and changeable (paired with the expression about women's hearts).
彼はすぐ気が変わるから、まさに『男心と秋の空』だ。
He changes his mind so quickly—truly 'a man's heart is like the autumn sky.'
恋愛の場面でよく使われる諺に『男心と秋の空』がある。
There is a proverb often used in romantic contexts: 'a man's heart is like the autumn sky.'
昔のことわざだが、友人の気まぐれを見て『男心と秋の空だね』と笑った。
Although it's an old proverb, seeing my friend's whims we laughed and said, 'a man's heart is like the autumn sky.'