Aki's father was sexist and believed that women could not lead or be put in important positions; so even though she was the rightful heir, he wanted to make his half breed son his successor.

So, even though Aki never asked him, Noriko killed both Takeshi (Ali's father) and his current wife, who was not Aki's true mother. He then announced Aki as her father successor.

For this reason, Alexei and Anastasia (both of Aki's half siblings) have formed a rebellion against Aki and the Katsu empire.