Number Contract (数契約; suu-keiyaku) is a family introduced in BS63, possessed exclusively by the Contract card The PartnerCat Fermat, and the Golden Cloud family cards with Contract Advent that supports Fermat.
The family name originates from the design of Fermat being a mathematician while being a magician in the lore. She believes that the universe is formed by numbers, and has the image of a scholar. Her name, Fermat, also references the famous mathematician with the same name. Cards in the family are either direct power-up forms of Fermat, like The HeavenCountSorceress Fermat-Searam, or spirits with mathematician/mathematics motifs.
