At the time of Corrin’s kidnapping, ages were as follows: 

Yukimura, 25; Ryoma, 13; Corrin, 5.

Corrin comes back after 14 years. (19 years old at Fates start)

Sumeragi’s death left a wife with no clue on how to rule and a son too young to do so. 

Yukimura becomes the de facto leader of Hoshido until Ryoma was old enough to assume his duties as prince. (Approx. 7-8 years)

Rumours circulate that Mikoto is just a puppet ruler and that Yukimura had ulterior motives for the crown.

A civil war troubled the country since there was no proper ruler. 

The civil war was not ended by Yukimura and Sumeragi loyalists but rather put on hold. Civil unrest still lurked in the hearts and minds of the citizens.

Saizo and Kaze’s father was one of the casualties of this war.

Eventually rival clans made their move at the peak of the Nohr & Hoshidan war by making deals with Nohr to take advantage of the weakened crown.

Despite Yukimura basically running the show after Sumeragi’s death, Mikoto still has to officially approve some of his decisions as ruler.

Which includes declaring war on Nohr.

To which she refused.

Mikoto decides to focus on reinforcing Hoshido’s defences. Her explanation is that the country is too weak without a proper ruler to guide them into war. Cue war-ready karakuri being made en masse to strengthen borders and the famous barrier that made Nohrians lose interest in invading Hoshido.

Azura’s kidnapping was NOT approved by Mikoto.

Yukimura still did it anyway and hired Shura’s gang to do it. He argued that the country needed a bargaining chip to have a shot at getting Corrin back.

Mikoto was not pleased. At all. She insisted that Azura be then treated as one of the royal family after negotiations failed.

He ends up being a father figure to the royal family.

Mikoto usually confides in him about worries in balancing being a ruler to a country she was not raised in and a mother to someone else’s children.

Usually the one to calmly talk to the kids about lashing out at Mikoto because ‘she’s not their mother.’

Manages to create simple toys for the children despite his busy schedule. Hinata especially likes them.

Like how Corrin sees Gunter, Azura and Hinata see him as the father they never had.

To the older children, Yukimura is more like an uncle or an older brother. 

Generally messy/unkempt appearance since he’s too busy running back and forth keeping the country together. 

He wishes he can stop and make himself look presentable for once but he never gets the chance in those 7 years.

He is actually really conscious of his appearance but is somewhat resigned to his unkempt state since he’s so busy.

7 years of running the country by himself also made him dependent on a cup of coffee to keep himself going.

He’s used to being busy.

Post-war Yukimura still does his duties as advisor to the crown as he did before but has considerably less work thanks to Ryoma.

More often than not, he’s at loss as for what to do now that he has free time.

OC Related

For roleplays and stuff that require OC interaction. 

(YUKIVES) His relationship and eventual marriage to Yves Prospero was a controversial move. 

Rumours that she had ulterior motives never stopped circulating. They still lived happily despite that.

He sees Yasuo as a younger brother.

Like Yukimura, Yasuo became Sumeragi’s disciple and as a result the two grew close- forming a brotherly bond.