For Rin and Sakura, there were no choices for them in the first place.

One of them has all elements, having five multiple elements as her alignment. The other has no elemental alignments, having Imaginary Numbers only. Both sisters have a rare potential that can be equated to miracles. This had surpassed the limits of so-called natural talents or inborn skill; it is almost like a curse.

- Fate/Zero: Act 12, Part 3