[Klashikari]

Originally Posted by Malkuth

Wait in Tsukihime Touno and Nanaya had the same ability ... give or take, right?

Spoiler for Tsukihime, End of Arcueid Route:

No, SHIKI does NOT have the Mystic Eyes of Death Perception.
He basically sees the lines of Life. If he disrupt them or drain them, it is equal to death.
The real Mystic Eyes of Death Perception affects the origin of all things, the "flaws" within any entity, living beings/objects alike and allow the user to annihilate its existence itself. SHIKI's Magan use the same concept of "lines", therefor, SHIKI/Roa thought they have the exact same ability than Shiki's but he was utterly wrong from the very beginning.

The former has no effect against objects and basically kill as if it was a life force draining skill, while the later obliterate literally the target.
This is the reason why Shiki says the famous quote

"I'll show you what it means to kill things"