There was precedent, of course, for succession in the event of the untimely demise of the incumbent ruler. Between political intrigue, ambition and necessity - and these qualities have never been in short supply within the ruling classes of the Fire Nation - history contains no shortage of examples.
Deposal in the absence of bloodshed, however, is another matter entirely: and more so when the Heir Apparent is the banished prince, who has, contrary to every expectation, found the Avatar and brought him home.
He'd been given to understand that petitioners had begun arriving at the palace immediately that the fires had been put out, to make their pleas to whom-they-knew-not. Speculation in the courtyards and the corridors had been muted but persistent; it was much, much later that he learned that Mai's arrival had done nothing to dispel the rumours and wild guesses. (Summoned to take her place at the prince's side, it was muttered, but alive or dead? Ah, that was the question.)
(Lying on their backs in the courtyard late one evening, staring at the stars, surrounded by silent guards, Sokka had told Zuko dreamily and disjointedly about ice-dodging. Zuko was himself too exhausted for certainty, but he suspected that Sokka thought he was talking about the negotiations.)
Factions loyal to his uncle, to his mother, and to the Avatar began to make themselves known from the background of loyalty to the old regime. By day, Roku advised him through Aang: structural reorganisation of the Fire Sages proved easier than Zuko had dared hope. Alone at night, the princeling spoke aloud to the empty air - to his uncle; to his mother; to Mai - begging guidance and forgiveness. (Sometimes he dared hope that the whispering sighs he heard in the early hours were more than the creak of old buildings and the passing breeze, though he knew it could not be.)
He wrote to his uncle most evenings, and in return received one infuriating letter each week detailing the minutiae of the Jade Dragon Pai Sho league; of the regular customers and their interactions; and elliptical remarks regarding the Ba Sing Se court intrigues in Kuei's absence, followed from the periphery. (Many years passed before Zuko realised that this was Iroh's way of offering advice.)
On another day, she woke in the grey morning light to find Mai framed in the doorway regarding her coolly, guards bristling on either side. "Why are you doing this?" she asked, and Katara slipped with a groan from her bed, dismissed the soldiers with a wave of her hand, and took to the deserted corridors and hallways to talk with her erstwhile enemy.
But not just yet: because now, now it is dawn on the day of his coronation, five ruthless weeks after the passing of Sozin's Comet. Zuko is still stiff and slow as he moves through his quiet morning routine of meditation and stretches; as he bends to the mountain of paper thrown up overnight; and in this way three hours pass. He is interrupted by newly-appointed palace staff bearing formal robes, who prompt him to dress; he waves them out with his good hand.
He is half-way - the easy half - to dressed when he hears her voice, and turns to see her leaning against the doorframe, drenched in sunlight. She smiles at him, gentle and wry, and he is speechless with confusion and relief and joy and the warmth of the sun on his back.
Aang and Zuko regard one other for a long moment (in this dark and lofty room; in the quiet before the storm, Zuko thinks, in some distant reach of his mind). They say, quietly, what is necessary; they embrace; and together they walk out into the light.