Infinity
It is mathematical fact. An impossibility. One can never divide by infinity.
Infinity stretches on in both directions in a plane, spanning all the positive and negative numbers one could ever imagine. Infinity stretches on in both directions in life, spanning all the deaths and births one could ever live through and experience.
To try and intercept the concept of infinity, one would draw an asymptote. The space between a line and the asymptote, life and infinity, will always exist. As a rule, therefore, the two lives will forever live on, yet will always be dependent on one another to exist. One is immortal, the other a pawn to living life for what it is worth.
As Kabuto leaned forward and brushed his pale fingers against the large tome open on the lab desk in front of him, he was silent in his thoughts. His golden eyes were seemingly transfixed on a specific spot, uncharacteristically distracted from his work as he stood still.
His eyes paused at the center of the chemical equation written out before him. Double arrows meant equilibrium, and he knew well that Proust in the ninteenth century had developed a law, a scientific fact. One could move from the products to the reactants, and in reverse, and repeat the chemical equation once balanced... and it would always yield the same results, the same elemental composition, for an infinite number of times if done correctly.
A single thin finger pressed against the double arrows separating the equation on the page. Pointing in both directions, almost as infinity. Ever-reaching, forever living on.
He snapped out of his thoughts for a moment then, and straightened up. As he flexed his fingers, weary eyes glanced down at the tiny scales that were in the process of forming on his skin, and he mused to himself:
"...I am infinity, it would seem."