During the time Rostam and Rosalyne had met, come to know each other, and grown close, they had faced many external challenges. But under their careful planning, everything had been moving in a positive direction.
Though Khaenri'ah could fall at any moment, unleashing hordes of monsters upon Mondstadt, they had prepared well in advance. Grand Master Arundolyn was defending the border with extensive fortifications, sure to hold back the monster tide. Rostam remained in Mondstadt, ready to deal with any creatures that slipped through. Everything was in place. All operations were proceeding as planned.
If nothing went wrong, Rostam believed the Knights of Favonius would win this war. Then, as a hero, he could marry Rosalyne and give her the happiness she deserved.
Everything was moving toward a bright future. But no one expected that, at this critical moment, the first problem would come from Rosalyne herself—the one who had been by Rostam's side, helping him with administrative affairs.
That afternoon, upon returning to the Knights' headquarters, Rostam witnessed Rosalyne engulfed in blazing flames that consumed her fragile body and everything around her. Even the Grand Master's office was melted by the scorching heat. A surge of Pyro energy erupted—so powerful that even Rostam was stunned.
But then he thought of Rosalyne, trapped in the inferno. Amid the chaos, amid the shouts, he charged into the flames without hesitation, using all his strength to withstand the fire as he searched desperately for her.
At last, through the searing heat, he found her burning hand and pulled her scorching body into his arms. Enduring the flames, he carried the unconscious Rosalyne out of the blaze.
Though he had saved her, she showed no improvement. Her body still churned with raging Pyro energy, burning her from within. She remained unconscious, and Rostam grew frantic.
Only when Rosalyne's family arrived and explained her condition did Rostam learn the full truth. Since birth, Rosalyne had possessed innate Pyro power. Moreover, as she grew, her body absorbed surrounding Pyro energy uncontrollably, storing it within herself. Over time, she became like a vessel filled with Pyro—ready to erupt at any moment, consuming everything around her and even threatening her own life. If she could not purge or control this power, she would eventually be devoured by the flames, becoming a puppet of the elements.
To save her, her family had sent her to the Sumeru Akademiya to learn how to control her Pyro. Not only could this prevent the flames from harming her body, but it could also grant her great power. During her year at the Akademiya, Rosalyne had indeed learned a great deal—simple methods to control the elements, as well as many other fields of knowledge, making her a learned and talented young woman.
A fortnight ago, driven by homesickness, she had left the Akademiya to visit her family and returned to Mondstadt. There, she met her destined love, Rostam, and fell into a passionate romance.
According to plan, Rosalyne, who had not yet fully mastered her Pyro, should have returned to the Akademiya as soon as possible to seek further help. But seeing Rostam so burdened with work, she could not bear to leave him. She wanted to help him with his duties and lighten his load. She delayed her return—again and again—until her Pyro power finally erupted, and she understood the seriousness of her condition.
Realizing all this, Rostam looked at Rosalyne, unconscious and tormented by the flames. His heart ached with pain and guilt.
He resolved to send her to the Akademiya at once, to let the scholars there resolve her Pyro troubles. Before she departed, he exhausted all his power to temporarily suppress the raging elemental energy within her, allowing her to regain consciousness.
The moment she woke, Rosalyne saw Rostam's pale, drained face and understood what had happened. She took his hand, her voice filled with shame. "I'm sorry—I wanted to help, but I only caused you more trouble."
Still weak, she apologized repeatedly. Rostam held her hand and gently caressed her cheek. "No, it's not your fault. If not for me, you wouldn't have delayed returning to the Akademiya. I've arranged a carriage and a knight escort to take you to Sumeru."
In truth, Rostam wanted to escort her personally. Only by seeing her safely arrive at the Akademiya could he truly rest easy. But that very day, urgent news had reached the Knights.
The ancient nation of Khaenri'ah had suddenly fallen. Countless monsters were surging from beneath its ruins, ravaging every land they crossed and attacking every person they encountered.
With Grand Master Arundolyn holding the front lines, Rostam could not abandon Mondstadt's people for personal reasons. It would betray both Mondstadt and Arundolyn. At this critical hour, Rostam had to stay and lead the Knights in defending the city.
Rosalyne, intelligent as she was, understood without further explanation. She knew how vital Rostam was to Mondstadt now.
So she did not refuse. Instead, she said softly, "Before I leave Mondstadt, I want to sing you one last song. And—do not forget our promise."