Short version:
A long, long time ago, the Federation had a marshal who chased down space pirates and beat them so badly they nearly hid in a black hole.
Then the marshal retired in glory, faked his death, and changed his appearance.
He planned to enjoy retirement under another, completely unknown identity.
But because he was so beautiful, space pirates abducted him and made him their chief's wife.
The pirate who abducted him was the very one he'd chased and beaten for so long...
Full version:
To honor a promise he had made to his teacher, Jiang Ruxue defeated the rotten Imperial Army and gave his life to protect the Alliance, winning it a bright future.
Everyone in the Alliance believed their marshal had died in battle.
In truth, after his spirit form self-destructed and his body was badly injured, Jiang Ruxue's appearance changed dramatically. He hid on a desolate planet, hoping to die in peace.
If he could live a somewhat normal life before he died, he would have no regrets.
But fate had other plans. His old rival, Aiden, the ruthless, merciless pirate chief who killed without blinking, landed on the same desolate planet.
Fortunately, they had fought from inside their own warships, so Aiden didn't recognize him.
Unfortunately, Jiang Ruxue was attractive enough to win Aiden's love at first sight, and was "forcibly abducted as a husband."
And so began the former Alliance marshal's life of pretending to be a delicate guide and keeping his secret identity under wraps...
*
The pirate chief, Aiden, was vicious, cruel, coldhearted, and guilty of every imaginable crime.
But he had a secret.
Back when the Federation chased him down and nearly forced him into a black hole, he had done it on purpose.
As long as Jiang Ruxue could secure his place in the Alliance, Aiden wouldn't have minded being his stepping stone a hundred times over.
His subordinate complained, "Boss, why go to all this trouble? You've invested so much, and you haven't even met him. That's not how unrequited love works."
Aiden took a long drag on his cigarette. "Shut up. What would you know?"
But later, all he heard was that Jiang Ruxue had sacrificed himself with his ship.
He drifted through life in a daze, until he met someone again who looked nothing like Jiang Ruxue, yet somehow seemed familiar in every way.
*
Jiang Ruxue's spirit form had disappeared. Aiden carefully avoided bringing it up, afraid of reopening his wounds.
And what made him tear his hair out most was that Jiang Ruxue seemed not to care about him at all.
After trying everything he could think of, the pirate chief was so heartbroken he began to question his own existence.
That was, until Jiang Ruxue got drunk.
A fluffy little head poked out of his collar. It meowed at Aiden, then gave him a coquettish look and showed off its white belly.
PS: This story is set in an Omegaverse-style guide-and-sentinel world.
Theme: Love life.