Ok... quick guess is that Sakuya is using silver knives, Shion being a poverty goddess means that the silver is pushed away since otherwise it could be considered gaining 'wealth', and Shou is attracting the knives for the same reason due to her own power of gathering treasure.
Ok... quick guess is that Sakuya is using silver knives, Shion being a poverty goddess means that the silver is pushed away since otherwise it could be considered gaining 'wealth', and Shou is attracting the knives for the same reason due to her own power of gathering treasure.