You ever lie awake at night and think about how intimate GinHiji is? Like yeah everyone and their grandmother already knows that they’re narrative foils and all that, but do you ever just. Stop. And think, “Wow, when Gintoki looks at Hijikata, he sees a version of himself that never lost?”
Of course, Hijikata has lost things (his place with his brother, a home), but he hasn’t lost his general. He certainly hasn’t had to kill him with his own hands.
And that parallel is made very obvious in the Farewell Shinsengumi arc, but once you read through the manga again, it’s clear that Gintoki has been at least somewhat aware of this parallel from the beginning, from their second meeting on the rooftop, when Hijikata challenged him to a duel because he disgraced Kondou, his general, his comrade in arms. “Anyone who disgraces the Shinsengumi… I’ll make mincemeat out of them!”
Every subsequent interaction after that has just made the similarities more apparent, not only between themselves, but also between their respective groups: The Shinsengumi and the Shoka Sonjuku. The Shinsengumi and the Joui 4. The Shinsengumi and the Yorozuya.
And the last one’s important, because it shows that Hijikata doesn’t only represent what Gintoki was, he represents what Gintoki is trying to be again. He is not only the past, but the present, a kindred spirit walking the same road, who he can draw strength from. That is why their roads cross time and time again, not only in the serious moments when the Shinsengumi is at jeopardy (and isn’t it interesting how only Gintoki is present during the Mitsuba and the Baragaki arcs?) but also during the ridiculous moments, the goofy moments, where they’re just wreaking havoc in Edo, making connections, living life.
That’s why everything that happens to Gintoki ends up echoing around to Hijikata, and vice versa.
It’s Gintoki and Katsura pointing their swords at Takasugi at the end of the Benizakura Arc, saying, “We will cut you down!” to Kondou punching Okita during the Mitsuba arc, saying, “If one of us goes astray, the other two will beat some sense into him,” to Gintoki in the Shogun Assasination Arc, punching Takasugi, reminding him that he’s still a student of the Shoka Sonjuku.
It’s Kondou saying, “Why does he [Hijikata] always put the burden on himself? Always trying to play the bad guy,” to Takasugi saying, “We put the burden on you… You bore that sin,” to Gintoki telling Takasugi, “I don’t remember choosing you. All that happened was… I knew what he [Shouyou] held dear,” to Hijikata telling the rest of the Shinsengumi, “He told us to live… I don’t want you guys to die, that feeling is the same as Kondou-san’s.”
It’s how Itou’s death in the Shinsengumi Crisis Arc foreshadows Takasugi’s death in the Final Arc: Both are comrades in arms who had gone astray, but although they’ve made their way back to the right path, they’re already at death’s door. Hijikata kills Itou in a duel to allow him die as an honorable warrior instead of as a traitor. Gintoki kills Takasugi in a duel in a way that allows him to die as a student of Shoka Sonjuku who succeeded in avenging Shouyou instead of as a vessel carrying Utsuro’s being.
It’s Itou telling Hijikata, as he grabs his hand to save him from falling to his death, “I hate you and one day I’ll kill you, so don’t die here,” to Takasugi telling Gintoki and Katsura as he saves them from falling to their deaths, “We may hate each other and try to kill each other, but still they’re bonds we can’t sever.”
It’s Gintoki helping Hijikata time and time again, reminding him who he is, delivering him things (spicy crackers for Mitsuba, a letter from Tetsu, a punch for Kondou), helping him get to where he needs to be… and Hijikata trying to return the favor as much as he can, running to Hagi to find him, delivering his bokuto in battle, kicking his ass over the gap so that he can make it to Shouyou, Shinpachi, and Kagura.
It’s Hijikata telling Gintoki, after finding out he’s Shiroyasha, “There’s something that only we can do. We can stop people from making the same mistakes we did.”