Ok, so I just got this little idea today, for some reason I got into a bit of a melancholic mood and this came to my mind.
I WARN EVERYONE WHO HAVEN'T READ THE MANGA: THIS CONTAINS SPOILER.
Well, I guess that's all, hope you'll enjoy it. :)

Disclaimer: I do not own Gintama, Sorachi-sensei does

Why was she running towards him instead of abandoning him and leaving him to die? Why did she struggle to reach him with all her might, not paying attention to her injuries, to the warzone around her? Why was it that he was the only thing left in her mind, his thoughts filling her brain? She had no clue.
Why was it that no matter how far she reached her hand he couldn't catch it?
Why did she want to save him so, so badly when she'd sworn to be the one to put an end to his life? It was her duty… Why couldn't, why didn't she fulfill it? She didn't know.

And most importantly: why, oh God just why did he have to die?

He didn't kill her when he should have, he took her to his home, raised her, shared his meals with her, so that they wouldn't be alone…
He gave her such a wonderful name.
Why couldn't she fulfill her duty? And once she decided to go against his will and protect him instead… just why couldn't she save him?
She had no answers.

These were some of the thoughts of Imai Nobume, former Vice-Chief of the disbanded police force, the Mimawarigumi.
But she was not really depressed. The day she bid farewell to her beloved father-figure, she took upon herself another duty. She promised herself, that she would carry through the task Isaburou has left; she would see the rise of the sun above a new country. As the subordinate of that man it was her responsibility.
And as a disciple of Shouyo, she had to do what all the other pupils did: fight Utsuro and protect his soul. The very soul of the man which has turned her so weird that she's not been able to kill her target anymore...
This duty was hers to fulfill, one she has decided for herself.
That's why she told the other disciples about Utsuro, that's why she brought them all together and had them sail out to the vast universe to fight their battle.

With both the hoodlum and elite polices of Edo gone, and this time with the Yorozuya also gone, she was left behind to handle things on Earth and protect their town till they'd return to create the place Isaburou had dreamed about.
She lived in Yoshiwara, to where more and more people have fled to hide from NobuNobu, and the more men settled down in the outlaw underground city, the more her strength could help the Hyakka. She helped people escape the Shougun's grasp to join with the rebel forces; she tried her best to preserve the Edo the others who had left loved so much.
After NobuNobu had also travelled to the space the rigorous research after criminals like herself decreased, but after a moment of delusive peace the Liberation Army has arrived to Earth, thus getting even the average populace in danger after blowing up the Terminal. The country has crumbled, the government has also crumbled. No matter how much she has saved and how much she, and everybody else left in Edo have struggled, the fight seemed endless. But they weren't dead yet. The samurai of this country were not dead. And they will survive…

Sometimes she was thinking about Isaburou and how it would be different if he was still around.
She thought about the Shinsengumi and how unnerving their abcense was.
But mostly she thought about those who have taken her request to defeat Utsuro. When would they be finally back? Because they would get back, that was no question. That man, who resembled Isaburou so much would surely not die before accomplishing what he has taken in his head. Everyone has been leaving job requests and money for them, everyone has been waiting for them to come back finally...

She heard that the Liberation Army was chased out of Kabuki district, while she was busy tracking down Utsuro's whereabouts, and she had a pretty good guess who must have led the people. She felt relieved…
After negotiations a cease-fire was to be installed, so the head of the Liberation Army decided to halt their movements. It looked like the Naraku wasn't too fond of this development of events, so they disguised themselves as ordinary townspeople and started attacking the garrisons to stir the war.
She was following some of them when they attacked a little group of three people and a dog. She let herself a little smile before she interrupted their fight and took a good look at them. They all looked just fine, and he, well he still had the same dimwitted face with those dead-fish eyes, so alike his.

'Isaburou, even if you're not here, I think that… I am, no, we are going to be alright now. The man that's so like you, the Yoruzuya has finally returned'

So I hope you liked it, please let me know what you think. Thank you and you're awesome! ^.^