Kuraba Touma is Okita Mitsuba's fiance. He pretended to ask for her hand in marriage in order to get close to the Shinsengumi and manipulate them from behind the scenes in order to facilitate his own illegal dealings with Joui extremists.
In the end he was eliminated by Okita Sougo in a Shinsengumi raid during his military arms transaction with the Jouishishi extremists at the harbour.