Gengai builds a time machine and the Yorozuya decide to use it to go to their own pasts, but because it's Gintama, something goes wrong. The Yorozuya ends up in the Shinsengumi's pasts and Okita in Kagura's. Stuck for who knows how long, they learn things about each other. How will they screw up, or even help, each other's lives? (Implied Okikagu, T for Language, Title will change)