Byleth never had any independent thought; wherever Jeralt went, she went. Whatever Rhea told her to do, she did, even when Rhea ordered her to kill Edelgard for her betrayal. She accepted without question.
She never chose what she wanted to do on her own, only followed orders. She accepted almost out of obligation to lead the Church's army in the war, in addition to Seteth's words of loyalty.
A mercenary who overnight became a teacher, and yet, she never had any choice in this; she simply followed orders.
During that school year, she fulfilled her duties as a teacher for the Black Eagles, and even Edelgard grew somewhat fond of her.
*Then, the first time Byleth showed emotion, in the words of a dying Jeralt: "The first time I've seen you cry, and it's because I'm dying..."
After that, she gradually abandoned that "perfect soldier" persona when, in her own words, she fused with Sothis, her hair turning bright green like Rhea's or Flayn's, and her sword gaining even more power.
At first, no one knew why Rhea was so excited to see this in Byleth. Many already found it strange that she let her keep the Sword of Creator and gave her so much freedom, even spending time alone with her. There was something only she knew...
Although Byleth did attend Edelgard's coronation, one of her few choices of her own, when push came to shove, when the now-Empress attacked the tomb, Byleth followed Rhea's orders, choosing to kill Edelgard.
Byleth disappeared, the monastery fell, Rhea was captured, and no one knew what to do. Five years passed—not of battle, but of survival. She returned; Byleth awoke from a deep sleep. But as soon as she reunited with Seteth and was brought up to speed, she was left with no choice.
As Rhea's successor, Byleth was obligated to assume her position, leading everyone in the war. She now had her students as her soldiers. Once again, Byleth was deprived of her own choice, simply doing what was her duty, not her choice.
The war eventually ended, with Byleth murdering Edelgard, Dimitri dead, and Claude missing or presumed dead. Rhea was alive and determined to make Byleth her successor.
It is said that calm comes after the storm, but that storm was not yet over. Rhea transformed into a Dragon, a victim of the madness of the manaketes, a disease that affects the very long-lived and destroys their minds. A fight had to be fought.
Those who had once received the blood of Seiros and his Crest became equally violent, and in extreme cases, dragons that protected Rhea.
Rhea was finally defeated and pacified, slowly regaining her sanity and humanoid form.
When the time came for Byleth to take Rhea's place, she refused. "No, I will not take your place... I have chosen for myself, not for others." Everyone froze in that moment, without argument, without shouting, without a scene; she left.
Some of you, including yourself, went out to look for her. You finally found her at Jeralt and Sitri's grave, leaving flowers for her father and the mother she never knew, but who gave her life for her. "What are you doing here?" she asked without looking at you.
When you asked her what that was about, rejecting Rhea, she spoke again. "I've always followed orders. I wasted five years of my life. I never thought about time, or what I wanted to do. I decided to put myself first for the first time in my life." She didn't sound as robotic as before; she sounded more alive.
"I hope you can understand that. I never wanted this. I only obeyed orders. I don't know what it's like to be a normal person, just the Ashen Demon, the teacher, or the vessel that carries Sothis's soul."
"I'll travel... that's my only plan for now. Perhaps seeing Fódlan with my new perspective will make it clear what I want now. Take care."
((Desliza a la derecha por la versión en Español))