Tatsuya Shiba, eldest son of the Yotsuba Clan, was born to Shiba Tatsurou and Shiba Miya shortly after the clan's devastating Nightmare of 2062. This event claimed nearly half their members and left his aunt, Yotsuba Maya, infertile. His younger sister and only sibling, Miyuki Shiba, shares the same school year despite their eleven-month age difference, often leading to them being mistaken for twins. Initially hailed as a potential protector, the clan later feared Tatsuya's innate abilities, prompting some branch families to demand his elimination. His grandfather, Yotsuba Eisaku, intervened, instead training him as a combat magician and strategic asset. Following his mother's death and his father's remarriage, Tatsuya and Miyuki relocated to Tokyo under clan orders. They reside in an oversized home featuring a private magic engineering lab funded by Four Leaves Technology. Standing 175 cm tall at high school entry and later reaching 180 cm, Tatsuya possesses an athletic build. His appearance is often perceived as ordinary or austere, marked by dark hair, uneven bangs, and strikingly piercing blue eyes – a stark contrast to Miyuki's renowned beauty that frequently obscures their sibling connection. He maintains a consistently stoic demeanor, rarely displaying overt emotions. This emotional suppression stems from an artificial magician experiment conducted on him at age six by his mother and aunt. The procedure installed a secondary Magic Calculation Area by altering his limbic system, enabling systematic magic use but eradicating his capacity for strong emotions like fear, hatred, envy, or love. The sole exception is his profound devotion to Miyuki's well-being, manifesting as extreme protectiveness and ruthless action against perceived threats, earning him the "siscon" label among peers. Despite his emotional limitations, he shows kindness to friends and occasionally engages in teasing. His unconventional upbringing as a living weapon resulted in social ineptitude, frequently causing him to misinterpret typical teenage interactions. Magically classified as an irregular, Tatsuya's innate Magic Calculation Area centers on three unique abilities: Decomposition, dismantling matter/energy or erasing magical sequences; Regrowth, restoring objects/organisms to a prior state within 24 hours; and Elemental Sight, perceiving and analyzing information dimensions like eidos. The Yotsuba deem these abilities "fake magic" as they destroy or restore information rather than alter it. His artificial Magic Calculation Area allows systematic magic casting, though significantly slower and weaker than natural magicians. However, his psion count is the highest known, enabling advanced techniques like Gram Demolition and Flash Casting. Combat-specialized, he excels in long-range precision attacks, including over-the-horizon sniping up to 1,200 meters, and close-quarters combat via ninjutsu training under Kokonoe Yakumo. This training grants non-magical presence sensing, chi utilization, and techniques like Through Strike and Shukujihou. His strategic-class magic, Material Burst, decomposes matter into pure energy, yielding nuclear-scale explosions. As "Taurus Silver," he excels in magic engineering and CAD development, creating devices that enhance others' magical capabilities. Tatsuya's status within the Yotsuba Clan is complex and contentious. Born the apparent heir, he was demoted to Miyuki's guardian after her birth revealed his "non-standard" magic. Many deny his legitimacy as a family member due to his inability to wield conventional magic. Yet, his combat prowess secures his role as the clan's primary enforcer. His engagement to Miyuki, the designated next clan head, cements his position, though traditionalists still view him as an outsider. His feared military reputation is reflected in codenames like "Mahesvara" (referencing Shiva) and "God of Destruction." He operates under aliases such as Ooguro Ryuuya for clandestine missions. Throughout his development, a pragmatic drive to change the world persists, fueled solely by his commitment to Miyuki's safety and happiness, not personal ambition.