expression
all girls eventually awaken to sex
Proverb meaning that even the most sheltered or innocent girl will eventually become aware of sexuality, just as a bean pod hidden in the shade will eventually burst open when ripe. The literal image is of a bean pod in the shade bursting open.
See also: 豆
「陰裏の豆もはじけ時」ということわざがある。
There is a proverb that says, 'Even the bean in the shade will burst open in its time.'
The word 豆 (bean) is used metaphorically here to refer to a girl's sexual awakening, a sense listed as sense 3 of 豆.
A traditional Japanese proverb. The exact origin is uncertain, but it draws on the natural image of a bean pod bursting open when ripe, even in the shade, as a metaphor for inevitable sexual maturation.