Ryuunosuke Uryuu

Birthday: January 31
Height: 174 cm
Weight: 65 kg
Blood type: B

The master of Caster, Ryuunosuke is a serial killer who summons Caster after murdering a family and using their blood as a component in the summoning ritual. Though he is not a magus, he was selected by the Holy Grail to fulfill the war's requirement of seven Masters and seven Servants. Ryuunosuke knows nothing about magic or the fourth Holy Grail War; his involvement in the war is simply to watch Caster kill people in unique and thrilling ways to relieve boredom.

(source: Type-Moon Wiki)