Yotsuba Clan

Biodata

Standing and Influence

• The Yotsuba are one of the ten families that rule Japan’s magical world through the Ten Master Clans system. Their influence reaches the military and judicial institutions despite the clans’ formal non-participation in politics. 1 21
• Other magicians regard the clan as mysterious, powerful, heretical, and dangerous. Following former head Genzo Yotsuba’s death, it became known as the “Untouchable”; Maya Yotsuba’s ruthless methods later cemented that reputation. 2 40
• By the time of Mahiro’s rise, the Yotsuba had surpassed their former parity with the Saegusa Family and stood alone at the top of the Ten Master Clans. 491
• The family formally took command of the Ten Master Clans after Mahiro’s unification proposal passed at the Master Clans conference. 493 494
• Its international standing is reinforced by Mashima Island, advanced research, stellar-furnace technology, and exclusive Knightmare technology. Reports also claim the island houses dozens to hundreds of strategic-class magicians stronger than the Thirteen Apostles. 618

History

Fourth Laboratory origins

The clan originally bore the surname Shiba before changing its name after joining the Fourth Laboratory. Unlike other research institutes that produced multiple magical families, the Yotsuba were the Fourth Laboratory’s sole surviving lineage and “crystallized result.” 617

This origin shaped the family’s exceptional magical traits: powerful specialized magic calculation domains and psychic abilities involving mental interference. These qualities attracted numerous political “investors” before Maya severed most outside influence. 617

Miya and Maya

Yotsuba Miya used Mental Structure Interference on her younger sister, Maya, converting part of Maya’s memories into knowledge to prevent her mental collapse. The intervention saved Maya but severed the sisters’ emotional bond; Miya’s repeated use of mental interference subsequently ruined her health. 249

To avoid another such tragedy, the family began training dedicated Guardians to protect and support its members. Sakurai Honami became Miya’s Guardian. 249

The clan’s history also includes extensive human modification. Shiba Tatsuya was born through in vitro fertilization after an embryo was implanted in Miya, while Miyuki was created as an adjusted human designed to inherit Miya’s talents and appearance. 249

Rise under Maya

Maya Yotsuba succeeded Genzo as family head and became the figure most associated with the clan’s feared public image. Though it was publicly believed that she could not bear children and that future heads would therefore need to come from branch families, Mahiro later emerged as Maya’s son. 2 348

Miya, long believed dead, was resurrected and publicly returned during the Yotsuba Spring Celebration, stunning the branch families and the wider magical community. 351 493

Organization

Main household

Branch families

The family’s known branch-family roster comprises the Tsukuba, Shiiba, Mashiba, Shibata, Kuroba, Takekura, and Shizuka families. The Shiba family is counted separately when Miya and Miyuki’s line is included. 351

• Tsukuba Family — Yuuka Tsukuba was a candidate for the family headship and is skilled in mental-interference magic. 25 350
• Kuroba Family — Performs sensitive work for the main house; it manages the Yamao Society, whose operatives can be treated as Yotsuba branch-family personnel. 19 350
• Shibata Family — Put forward Katsushige as a candidate for the headship. 351 352
• Mashiba Family — Expelled by Mahiro after opposing his succession; its assets were reclaimed by the main family. 354

Succession

The Yotsuba head is expected to be the strongest and most outstanding magician of their generation. 351

Maya convened the branch families for a Spring Celebration to choose her successor. The initial candidates were Miyuki Shiba, Fumiya Kuroba, Tsukuba Yuuka, and Shibata Katsushige. 351 352

• Fumiya withdrew and endorsed Miyuki. 352
• Yuuka and Miyuki ultimately supported Mahiro, with Miyuki explicitly acknowledging that she could not match him in magical power or technique. 353
• Maya declared Mahiro the next family head. 353
• At the succession ceremony, Mahiro accepted the family head’s authority, then immediately appointed Miyuki as his successor and made her president of FLT. 354

Assets and Operations

• Mashima Island — The family’s territory and location of its relocated main house. It serves as a center for Mahiro’s projects and the family’s growing military and technological influence. 244 617 618
• Arcadia City — A prosperous city on Mashima Island built with Yotsuba resources; its administration and unusual population became a source of resentment among some branch families. 351
• Four Leaves Technology (FLT) — A Yotsuba-owned company. Its shares were treated as part of Miya’s inheritance, and Miyuki became its president upon assuming the headship. 250 354
• Assassination and covert forces — The clan employs the Yamao Society, an Assassination Squad, Shadow Garden’s numbered agents, and Arcadia personnel for enforcement and sensitive operations. 19 220 621
• Guardians — Dedicated protectors established after Miya’s decline; Sakurai Minami is identified as a Guardian connected to the Fourth Laboratory. 249 493

Political Relations

• Ten Master Clans — The Yotsuba led the clans into a unified structure under Mahiro’s initiative. The Saegusa and Jumonji families openly supported the proposal before the vote passed. 493 494
• Saegusa Family — Formerly considered one of the Yotsuba’s “Twin Pillars” within the Ten Master Clans. Saegusa Koichi backed the Yotsuba unification plan after Mayumi declared her support. 22 493
• Jumonji Family — Katsuto Jumonji supported the Yotsuba proposal after learning of the family’s wider strength and allies. 493
• Japanese government / Toudou Aoba — Toudou is the family’s remaining sponsor. He demanded Mashima Island’s return and the transfer of Yotsuba research to government control in exchange for granting Lina a legal identity through adoption. 617