The Great Gintama Exhibition took place in Akihabara, Tokyo from December 23rd, 2016 to January 9th, 2017. A pamphlet was released at the event, containing some commentary by Sorachi. Here’s a roughly translated summary of some of the excerpts I found:
Farewell, Shinsengumi arc
Sorachi said he intended to write the past of the Shinsengumi and its formation earlier on, but that it would have been uninteresting to know everything right off the bat, so he postponed it to the Farewell Shinsengumi arc, where he finally decided that they’ll be “gone”. He described the arc as a “battle against fate”; meaning, considering that the Shinsengumi was based on the eponymous historical unit where the Kondo Isami died via execution, this arc was a race to see if Gintama’s own Shinsengumi would end up meeting the same fate in the end. Additionally, the arc began without a decision on whether Kondo himself would live or die in the end, but then looking at the results, he realized that he didn’t want the Shinsengumi to die, or that maybe, he just wanted his “own little chaotic world” to survive.
He also said he loved Isaburo a whole lot, and didn’t want to take him out the story, but claimed that there are deaths that even themselves can’t prevent. He said he cried like a mess when he was drawing him in his final moments.
Shogun Assassination arc
The concept for the Shogun Assassination arc, was planned very early on (which he also stated in Gintama vol. 66), and since the Shogun’s death was inevitable, he was aware that Gintama wouldn’t be able to return to its usual style and story structure once the arc began. So when he started writing it, he was prepared to end the series.
About Gintoki and Takasugi’s relationship with Shoyo, it was decided from the very beginning, and, since Gintoki always had a dead fish eyed expression, it was assumed that he might have suffered from traumatic experiences in the past. Sorachi said that he vaguely discussed with his first editor, Kohei Onishi, regarding Gintoki executing his teacher.
When Shoyo was captured, Katsura and Takasugi were sparring. Sorachi said that had Takasugi been there, he wouldn’t have backed down (from attempting to save Shoyo), but he would have died in the process.
Before he decided on a face to draw to Shoyo, Koichi Yamadera had already been chosen as his voice actor in the anime. He thought Yamadera was cool, claiming he was drawn by his voice, so he gave Shoyo a baby face that Yamadera didn’t possess, and the latter played his role with that in mind.
Rakuyo Decisive Battle arc
Sorachi said that as of the Rakuyo Decisive Battle arc, the rivalry between Gintoki and Takasugi still existed, and that Takasugi’s past crimes where never going to disappear, however, only Sakamoto had the skill to regard all of it as trivial matters and make them get along. He added that Gintoki, Katsura, Takasugi, and Sakamoto would never be all together again, and that each of them already knew this, but they could do nothing about it. So the fact that they only talked negatively about each other, made him sad. However, that’s also what made them so unique. He named them the Satcho alliance of Gintama*.
He also stated that he always intended to use the phrase “Katsura janai, Zura da!” at some point in the story.
He clarified that the scene where it looked like tears were flowing down Kamui’s face, was originally Kagura’s own doing. He wanted to leave the interpretation of the scene up to the readers, but assumed it would have been too hard to comprehend since he looked like Kamui himself was indeed crying. Additionally, he commented that if Kamui and Kagura had a real fight, Kamui would likely come out on top, however the point is, as long as the two of them are siblings, the older brother will never be able to defeat his younger sister.
Others
Gintoki is a man whose charm lies in the incomprehensible and puzzling aspects of his persona, and due to that, Sorachi was reluctant in drawing his youthful days. However, there were elements he couldn’t avoid, so he drew them little by little, sticking to as few boundaries as possible.
He heard a theory about Gintoki and Oboro being siblings due to the resemblance, but blamed it all on his poor drawing skills. He also asked if his second editor, Saito, doesn’t also looked like them. He wanted to draw a scene where the two of them said the same lines, but that had different meanings.
There was a commonly shared opinion among readers that, Takasugi was going to remain the final antagonist of the story until the end, but if that happened, Gintama would have been a smaller story about how “Sakata Gintoki settles/fixes his past”, so that idea was discarded early on. Finally, Sorachi concluded saying that the story of Gintama is about Gintoki and the Yorozuya, and the people that they met over the course of the story. A lot happened in the past, but he thought that it should be a narrative about how to live in the present.
*Alliance between the Satsuma + Choshu Domains formed in 1866 to restore imperial rule, and overthrow the Tokugawa Shogunate. It was brought forth through Ryoma Sakamoto’s mediation, who brought together Choshu leader Katsura Kogoro (real name Kido Takayoshi) with military leaders Saigo Takamori and Okubo Toshimichi of the Satsuma Domain.
Yorozuya Shinigami 