Board Thread:Questions and Answers/@comment-212.101.21.209-20151113105400/@comment-8695373-20151113111759

Yes, Hakumen is Jin from a timeline without Noel. He went back in time by jumping in the Kagutsuchi's Cauldron with Ragna and Nu. He sustained a lot of damage because of the Boundary and his memory was damaged, too. To help Jin, who could not even walk, Clavis Alucard offered him the Susanoo Unit, which kinda changed his personality.

During the Dark War he inwardly calls Ragna his brother. And he let Terumi to join them because of the same reason that Ragna thought of during his trip to the past:

(...Hm? Does that mean if I find Terumi and beat him during this current stage, the Black Beast won't be defeated?)

''Ragna suddenly noticed. If that were the case, he couldn't afford to kill Terumi. History would change.''