I'm A Failure As A Leader, And He's Also A Failure As A Leader

Gin and Hijikata find Gengai, who's newest invention is responsible for their body swapping. He tries to reverse the process but it doesn't work as something is missing. Gin remembers that part of his soul ended up in a dead cat which they must now find. Unfortunately, the Shinsengumi, with their new found freedom, and Odd Jobs, with their new strict codes, seem intent on getting in their way.