empress, queen, after, behind, back, later
后 centers on a female sovereign: an empress or queen. The meanings 'after', 'behind', 'back', and 'later' belong to a separate usage where 后 is used as a substitute for 後 in some contexts, but the core identity of this kanji is the royal consort.
后 originally depicted a person with a prominent mouth, likely representing a ruler giving commands. Over time it became specifically associated with a female ruler or consort. The use for 'after' is a later borrowing.
The top part looks like a crown or headdress, and the 口 inside is the mouth of the empress issuing decrees. Together they form the image of a queen.
For コウ, imagine a queen wearing a golden crown: the 'co' in 'crown' sounds like コウ, and she is the empress.
empress (consort); queen (consort)
empress (consort)
Empress Dowager; Queen Mother
Grand Empress Dowager, the Empress Dowager and the Empress Consort
Grand Empress Dowager, the Empress Dowager and the Empress Consort
retired empress; ex-empress; former empress; empress emerita
retired empress; ex-empress; former empress; empress emerita
empress (consort); queen (consort)
empress's palace; queen's palace
women's pavilion (of the inner Heian palace)
queen of heaven
Their Majesties the Emperor and Empress
empress dowager; queen mother
Grand Empress Dowager
empress dowager
queen
Her Majesty the Queen
empress's residence
Her Majesty the Empress