Ohi (Empress of the Imperial Family) (王妃 (皇族))
Ohi (empress) is the title of the Imperial family standing provided for queens consort of the Imperial family, or herself of such standing. The Imperial House Law stipulates that the empresses are the members of the Imperial Family in the article 5. The title of honor provided for the empress is 'Denka' (the article 23 - 2 of The Imperial House Law).
Since the secession from the Imperial Family of eleven of old Miyake (a house of an imperial prince) on October 14, 1947, there exists no Imperial Fmily who correspond to the Imperial Family standing of Princess.
Summary
While the title of the Imperial Family standing of prince or princess (of the Imperial Family) is attached after and treated as part of his or her own name such as 'Morihiro O' (Prince) in the case of the Prince Morihiro, a princess (and also imperial princess) is inscribed in such order of her husband's own name to come first, then his title, and then "hi" (queen consort) before her own name as 'Morihiro O [Prince] hi [queen consort] Shigeko Naishino [imperial princess]' in the case of the Imperial Princess Shigeko who married the Prince Morihiro. In terms of the official notation, it is improper to inscribe in inverse order such as 'Shigeko Ohi' (Empress) following other countries notation of king and queens.
In the case of the marriage of a member of the Imperial Family (an imperial princess or a princess); she becomes her husband's princess (until becomes an empress) and also continues to carry her original status.
Specific example of the above (as written in Japanese order): Terunomiya Sigeko Imperial Princess=>(Higashikuni no miya) Morihiro Prince queen consort Shigeko Imperial Princess=>secession from the Imperial Family=>Shigeko HIGASHIKUNI
An empress leaves the status of the Imperial Family member and loses the position as an empress upon the fulfills of any of these followings:
(The article 14 of the Imperial House Law)
When an emperor passes away and the empress wishes to part the Imperial Family.
When an emperor passes away and the Imperial Household Council approves the particular inevitable circumstances.
When she divorces an emperor.