One of the Three Founding Families, the Tohsaka family provided Fuyuki City as the grounds for the Holy Grail War. The distinguished magus family has long resided in Fuyuki, managing the leylines in the region. Although the family has been based in Japan for generations, its chants and incantations are recited in German. 200 years ago, the first head of the family, Tohsaka Nagato, was a pupil of Kischur Zelretch Schweinorg, one of the five living Magicians. Hence why the family still uses German today. Nagato’s ancestors were hidden Christians in Japan, which translated into Nagato having half-decent connections to the Holy Church. He was also well treated by the Mage’s Association due to his position as the pupil of a Magician.

Fate/Zero Animation Guide I: Glossary of the holy grail war I