The Sasaki family is as elite as it gets, and one of its members, Tetsunosuke, has joined the Shinsengumi.  He would have joined the Mimawarigumi, a police force with pedigree, but he is considered a troublemaker, which is why he was sent to the Shinsengumi.  Kondo assigns Tetsu to Hijikata as an assistant, so Hijikata is forced to endure the new recruit...
Like I've been saying, I am 
a fan of the Shinsengumi.
Como te he estado repitiendo, 
soy un fanático del Shinsengumi.
Como estava dizendo, 
sou fã do Shinsengumi.