After the previous empress' death, Sanaki was backed by the public in the year 640 to become her sucessor despite being just five years old, with the senate appointing senator Sephiran guardian to the young empress. It is later revealed that Sanaki was installed to be no more than a puppet for the senate in order to quell domestic unrest. However, thanks in part to Sephiran, both he and the young empress not only had the public opinion in their favor, but kept the manipulations of the senate at bay.

At first, he treats Ike and Elincia coldly and with disdain, but it is in fact a ruse, as he needs Ike's help in uncovering a Laguz slave-trading ring that other Begnion nobles are participating in.

After being confronted with the truth around Serenes Forest, Sanaki bowed her head to the herons and begged for forgiveness. Her intentions were deemed genuine enough that even Prince Reyson of Serenes felt their cold feelings toward the beorc lessen.

He escapes Begnion when the Begnion Senate, led by Duke Lekain of Gaddos, seizes control of the Empire; he subsequently forms an alliance with Gallia, Crimea, Phoenicis, and Serenes to reclaim her throne. Lekain later reveals that Sanaki once had an elder sister: only the firstborn daughter of Altina's lineage can hear Ashera's voice, they claim, and so Sanaki is a false Apostle. Sanaki later joins the Silver Army on the march on the Tower of Guidance. Upon defeating Lekain, he discards the title of "Apostle" and rules only as Begnion's Empress. Unlike her older sister (who is later revealed to be Micaiah), Sanaki did not inherit the brand and therefore he cannot hear the voice of the goddess Yune.