There has, in fact, been one successful restoration. Taika one.
Recapitulating the history: 5th century Japan had emperors who held real power and fought inside their family for it. A bunch of imperial princes were executed for treason.
When the survivors died natural causes and childless, the government had to resort to hunting down remote cousins whose ancestors had fled the fight for throne or settled in provinces as minor nobles - twice. Second time, in 507, Emperor Kinmei was a remote descendant (there have been suggestion that he was a complete impostor). From start of 6th century, the emperors were figureheads.
Until the middle of 7th century, when the family holding the real power (Soga, had gained it from Mononobe family by coup) was overthrown by an alliance of Nakatomi family with a prince Naka no Oe (then 19). Because of the strong tradition of figurehead rule, Naka no Oe refused throne when offered and ruled through figureheads till 661, when he did accept throne and started personal rule.
From 661 to middle of 9th century, emperors again ruled. But from middle of 9th century, emperors were again made figureheads.
Regarding empresses: Japan has had 8 empresses since 592.
But up to 8th century, the Imperial Family was largely inbred. There were some marriages between brothers and sisters (the first empress, Suiko, was daughter of Kimmei, married her half-brother Bidatsu and acceded to the throne after their brothers Yomei and Sushun had died), but mostly cousins. Emperors did also have concubines outside the imperial family; but having mother a member of imperial family was a required qualification to inherit the throne.
The empresses had been born into imperial family and been married to princes of imperial family. So all children of reigning empresses were also male line descendants of imperial line.
Also there has never been a husband of a reigning empress of Japan. The empresses were either widows by the time of accession, or never married.