Rokuro Inui’s 2014 Automatic Eve is a standalone steampunk novel. The 2019 English translation is by Matt Treyvaud.
A generation ago, tragedy struck when the Empress died in childbirth. Fortunately for the strictly matrilineal imperial family, her infant daughter survived. Better an infant empress and a regent than no empress at all!
Struck by a mysterious malady as a teen, the Empress is a recluse. The Shogunate is not displeased by this, as her seclusion leaves the administration of the nation up to the Shogun and his subordinates. They have no reason to fear that the Empress might actually attempt to rule. As far as the common folk know, the nation is ticking along just as it should.
Behind the scenes, however…