If it's anything it's a prequel, a good deal of the ideas and writing for the Kara no Kyoukai was further developed and used in Tsukihime. The Magan, Aozaki sisters...Mikiya plus Alpha is Shiki more or less.....
Kara no Kyoukai is considered to be Tsukihime prototype...
People say that it takes place in an alternate Nasuverse, but I'm not sure where they're getting that. Maybe because Shiki Ryougi's eyes don't suffer from the same problems and limitations as Shiki Tohno's? But that could just mean that Ryougi's more talented or something.
"Word Of God states that there can only be one user of the Mystic Eyes of Death Perception, which means either Tohno Shiki has them, or this Ryogi Shiki. In addition, Aozaki Toko's goal contradicts with the existence of the True Ancestor Arcueid, also from Tsukihime." http://tvtropes.org/pmwiki/pmwiki.php/Main/KaraNoKyoukai
Also, it's not a matter of skill. Ryougi's eyes work very differently than Tohno's, even though they have the same name. The Nasuverse is a snarl of alternate universes.
RaisingK said: "Word Of God states that there can only be one user of the Mystic Eyes of Death Perception, which means either Tohno Shiki has them, or this Ryogi Shiki. In addition, Aozaki Toko's goal contradicts with the existence of the True Ancestor Arcueid, also from Tsukihime." http://tvtropes.org/pmwiki/pmwiki.php/Main/KaraNoKyoukai
Huh? Weird, do they have source on their claim? I think I haven't seen that one in the novel. Also both Shikis cut the lines of death (and can see their "point" as well), they are the same, though it seems Ryougi Shiki's eyes (or to be more accurate, "connection") is a lot more powerful that Tohno's (explained in the 7th novel)
