Their relationship is about mutual respect. And he's good at his duties. It seems off for him to just step down, no one goes "OMG this person is way better than me!!, let me give up my responsibilities to them and yeet myself out"
It makes more sense for them to work together side by side as rulers.
Idk 乁( •_• )ㄏ
I think the reason he steps down is that he rules like his ansesters did and that has its flaws, where as Fl sees that even a commoners talents should be nurtured so that they can become a strength of the kingdome.. The old way is that only Nobels have influence and no matter how talented you are as a commoner that gets you nowhere.
Fl gives the commoners healthcare and education and nurtures their ability to help the kingdome hence strengthening the kingdome and Ml sees this. If Ml stayed as king then the nobels would stick to their guns and not alowe change, but if Fl was king they would need sound arghuments to diss the kings plans.
Spoilers.
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The Heroin is a total biach. She drugs FL and puts her in a room for a high ranking nobel too Tarnish her (hes fat and ugly and one of Heroins backer).
Ml comes in and stabs the creaps hand befor he can get into it with FL.
Heroin and her backers are all capture and executed (duno about the Queen downguard tho).
Ml and FL atend a funeral and later get married, Ml lets Fl take over some of his work and later he steps down as king and lets FL be the ruler as she was more capable than him.
Fl is Now the King of the empire and ml is her right hand man and goes to meetings she is to busy to atend.
Many male nobels arnt happy with the new system that prioretizes over all citizen health and way of lifer over the Nobels. These nobels are caught doing hady stuff and removed by the King herself.
Later Fl becomes pregnant and the first child is a daughter with Fl's eyes and Ml's hair.
Second child is a son with Ml's eyes and Fl's hair and third child is daughter with Ml's hair and FL's eyes but a bit lighter.
The citizens under FL's rule gained healtcare and education so even a slumm kid could grow up to become an emperial maid :P
Fl is put down in history as the ruler who nurtured her nation and the oldest daughter became the next King to rule.