How about a slightly angsty "what if" scenario?
It had been several months since the end of the war. Between his duties in Enbarr and Aegir, Ferdinand barely had time to stop in to see Dimitri. But with the seasons changing, and much to do as the summer began to pass, Edelgard insisted he take some time off.
And now he stood outside the door to the bedroom, with a rolling cart carrying lunch for two. He'd insisted on taking care of it himself.
"Dimitri?" Ferdinand called, knocking upon the door. "I have brought today's noon meal. May I come in?"
After a moment of silence, Ferdinand entered the room.
Sitting in bed, staring absentmindedly at the sky outside his window, Dimitri sat quietly. His hair hung loosely around him, having grown out longer since he'd been dragged off the plains and to this house. A patch covered his right side, hiding the damage left from battle that took the sight from his eye. Charmed cuffs were locked onto his wrists, keeping his strength tethered and keeping him from using magic to escape.
Though if he really wanted to, Ferdinand was sure the former King would be able to use the cane left for him as a weapon.
"I hope today's meal is to your liking," Ferdinand said as he prepared the tray. "Cheesy Verona Stew. It is a favorite of yours, if I recall correctly. We also have some delightful fruit cider, specially imported from Brigid. I think you will find it pairs well with the cheese."
Dimitri scoffed. "I doubt that."
"Ah, so he doth still speak!" Ferdinand smiled and set the bed tray on Dimitri's lap. "Here. Please, help yourself. Though, if this is not to your liking, I can have something else prepared-"
"Do you have to do that? Sound all reasonable and kind?"
Ferdinand paused. "I beg your pardon?"
"Don't. Lie to me." Dimitri warned. His blue eyes burned with heartbreak. "I will not hear of it.
"Why am I still alive?! Where the hell even am I? This is not a noble house that I recognize. Why keep me here? Why?! I should be dead! Why do you keep me here like some kind of pet?! You should have killed me!"
Ferdinand ducked his head just seconds before the bed tray was sent flying. The stew hit the wall with a sickening splash, the wooden bowl shattering to splinters. The spoon clacked on the floor, bouncing a few feet away.
"Dimitri, please-" he started.
Dimitri grabbed him sharply in an attempt to intimidate him. Ferdinand's hands instinctively moved to hold the prince in place, keeping him from pushing him around too roughly. With the cuffs on, Dimitri wouldn't have the strength to cause any permanent harm. But the fingers pressing sharply into his shoulders as he was pinned down told him it would still hurt.
"Why?!" Dimitri demanded. "Why didn't you kill me?! Why keep me here?! You've taken everything from me! My home! My family! My friends! What more do you want from me?!" Tears fell from his eyes. "You took everyone....Dedue....he....he was all I had left. You murderers-"
"He's still alive, Dimitri!"
Ferdinand kept his voice level. "I know things are confusing right now, but I need you to listen carefully. Dedue is alive. He is in another room, still receiving medical treatment. Once he is well enough for visitors, I will take you to see him. I swear it."
The grip on Ferdinand's shoulders eased, and the young duke took the opportunity to sit upright once more.
"He's still alive?" Dimitri asked softly.
"Yes, he is." Ferdinand gently reached down, removing the hands from his shoulders. "Dimitri...I made an appeal to Edelgard. You are here because of me."
"I...I don't understand."
"....Do you remember the night of the ball?" Ferdinand asked slowly.
Dimitri shook his head at first, before closing his eye and thinking. "Wait...we...we went to the Goddess Tower together."
Ferdinand smiled. "You do remember." He reached up, brushing the tears from his cheeks. "We promised each other that we'd live a happy, quiet life together?"
Slowly, Dimitri nodded. "I...I remember..."
"I swore I would make sure to keep our promise. So, I asked Edelgard to spare your life. She gave her word that if I could figure out the best possible alternative, she would agree to it."
Dimitri's face twisted in anger. "You made a deal with that woman?"
"I know you despise her. And I am not asking you to stop hating her." He pressed their foreheads together. "All I ask is that you rest and heal. And once things are settled, hear us out. Please."
Dimitri took a shaky breath, his hands reaching to grasp Ferdinand's shirt. "I...I wish I could believe you..."
"I know. I wish you could believe me too." Ferdinand smiled sadly. "But....until the day comes you can trust in me again....I will do whatever I can to ensure you are safe. I swear this to you."
He wished he could do more. But this was all he could do.
He hoped it would be enough for now.