|Spoiler Alert: This page contains spoilers. Read at your own risk.|
The Tooyama (十山) Family is one of the 18 Assistant Houses, bearing the number Ten (十) in their name.
They are part of 18 Assistant Houses, and are from the Tenth Institute, where the research focus was, "Wide-Area Magic that Generates Virtual Structures in Space as a Defensive Countermeasure to Heavy firepower". 
The development focus of the Juumonji Family was to intercept missiles and mechanized troops, meanwhile the focus of the Tooyama Family is aimed at defense of important facilities and the escorting of dignitaries after breaking through defensive lines. The duty of the Tooyama Family is to protect people during state functions, and due in part to this, they have the strongest relationship with the National Defense Forces among the 28 Houses. As a result, while participating apart of the Ten Master Clans system, they've never been a member of the Ten Master Clans. The Juumonji Family who are also from the Tenth Institute revealed this fact. 
- Family Head