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The Juumonji (十文字) Family is one of the Ten Master Clans, bearing the number Ten (十) in their name. The current Head of the Juumonji Family is Juumonji Katsuto. The previous Head of the Juumonji Family was Juumonji Kazuki. He stepped down during the Selection Meeting of AD 2097.
The Juumonji Families ability to wield multiple types of Area of Effect defensive magic has earned them the title "Stonewall". 
They are part of Ten Master Clans, 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 Juumonji Family is said to be not adept at gathering intelligence according to Katsuto. However, Saegusa Kouichi has complimented Katsuto's investigation on Anti-Magician media inciters to be very thorough. 
Kazuki, the former Head of the Juumonji Family is the owner of a Civil Engineering & Construction Company that contracts work with the Defense Forces. 
Area of Influence
The Juumonji and Saegusa Family's influence encompasses specifically the Kantō region and all of Izu. During the Master Clans Conference held every four years, the Heads of both families give a report on the status of the regions they monitor. 
The Juumonji Family's power surrounds the capital and can act regardless of jurisdiction. The Juumonji family is one of the three most influential families in the Ten Master Clans, besides the Yotsuba. 
It was mentioned that ordinarily the police would not have even been considered to be involved in incidents that involve the heir of the Juumonji Family. 
Published Data on the Juumonji Family shows that the Family's other members are a second son —— a Junior High Sophomore, a third son —— a Junior High Freshmen, and a daughter —— an Elementary School Fifth Year. 
- Former Clan Head : Juumonji Kazuki
- Children :
- Oldest Son : Juumonji Katsuto (Clan Head)
- Second Son - Junior High School, Eighth Year
- Third Son - Junior High School, Seventh Year
- Daughter - Elementary School, Fifth Year
Members of the Juumonji Family are specifically the only known individuals to lose their ability to use magic from a disease. 
The Juumonji family took the next step to hone their natural talent in spatial awareness. Their ability to wield multiple types of area of effect defensive magic earned them the title "Stone Wall".
That "disease" is resultant of repeated use of Over-Clocking. Overclocking is a technique that raises the activity of the magic calculation area in order to surpass his/her potential and temporarily increase his/her magic power. This is a technique for ensuring victory at the price of having your life as a magician shortened, the “Capitals Final Defense”. This is how the prior head of the Juumonji Family lost his ability to use magic, through repeated use of overclocking.
"Phalanx" (鐵壁) is a Move-Type Defensive Magic that isn't simply a sustained magic barrier, but a barrier that continuously refreshes itself. This is similar to a dense formation of heavy infantry that marches as one to increase the group's defensive power and then translates that power into an offense.
Phalanx is the famous technique of Juumonji family.
- ↑ 1.0 1.1 Volume 3, Chapter 6
- ↑ Volume 13, The Ten Magician R&D Institutes
- ↑ Volume 12, Chapter 10
- ↑ 4.0 4.1 4.2 4.3 Volume 17, Chapter 5
- ↑ Volume 11, Chapter 15
- ↑ Volume 2, Chapter 12
- ↑ Volume 18, Chapter 7
- ↑ Volume 4, Chapter 13
All items (3)