User blog comment:Godisme/Rain as a Blade/@comment-2048489-20111013171851

My theory on exactly how Tsukishima's ability works (please note, it is highly probable that this is speculation). This is looking more and more like what The 3 emps of Yliaster did in Yugioh 5ds. Whenever Tsukishima cuts something, he slips himself into its past and creates an alternate timeline that applies only to the affected object, changing history so that he has been around that object in some way. With this, he changes history and lays a trap in an area, changes history so that he has fought Byakuya's sword many times WITHOUT AFFECTING BYAKUYA'S PAST. In this way, the unaffected are aware of how things "really were", but at the same time, the alternate timelines that Tsukishima created also technically occured. Everything is convinced that the alternate timeline that applied to them happened because they DID happen, for their alternate reality. Tsukishima becomes aware of the target's timeline because he "lived" alongside that timeline. For himself and everything he affects, he was always there. Literally.

And for when multiple people are aware of the same reality, Tsukishima could easily have slipped himself into their reality in a way that allows the facts of two individuals' timelines to overlap.