Can this character be considered a slider? (Haruhi Suzumiya books 9&10 spoiler)
The only character which can be considered an actual Slider (https://en.wikipedia.org/wiki/Interdimensional_being), albeit temporarily, is Kyon. He was the only character (an actual person, rather than a temporal construct made by Haruhi as Yasumi was) who experienced first hand existing in two different dimensions during the events of the 4th novel(the disappearance of haruhi suzumiya).