In his original form as the Silver King, Adolf K. Weismann is portrayed as a tall man with a youthful complexion, knee-length silver hair, and gray eyes. His straight hair featured a distinct lock that fell to the right side of his face and split into two strands. His usual attire consisted of a formal dark green double-breasted coat with large cuffs, storm patches, and moss-green lining, worn over a white ruffled shirt. He paired this with dark green trousers and plain white shoes, giving him a refined, aristocratic appearance.

Several decades earlier, during his time as a German researcher, Weismann wore his hair at shoulder length, flipped outward and parted to frame his face. He typically dressed in a German military uniform with a white laboratory coat layered over it, along with a red and black armband on his left arm. Beneath the uniform, he wore a yellow shirt and a green necktie.

After losing his body to the Colorless King and inhabiting a new one, Weismann assumed the identity of Yashiro Isana, appearing as a thin Japanese teenager of average height with messy white hair and light brown eyes. Initially, he wore a standard navy blue school uniform, consisting of a high-collared jacket, loose trousers, a long-sleeved undershirt, and brown shoes. Upon unofficially enrolling at Ashinaka High School, he adopted the academy’s uniform, which included a white shirt with a red ribbon, a black jacket with the school’s gold pin, and rolled-up trousers. He retained his brown shoes, worn without socks.

During this period, Yashiro was frequently seen carrying a distinctive red Japanese parasol, decorated with a cross-like green pattern outlined in gold near its top.

Later, after his body regenerated in the Schattenreich, he once again wore his formal Silver King attire, this time tailored to the proportions of his younger form. By the conclusion of the conflict, Weismann returned to his original body, reverting to the hairstyle he had worn over seventy years earlier.

As a researcher in Germany, Adolf K. Weismann was characterized by his optimism and idealism, approaching his experiments with enthusiasm and the belief that he and his sister’s work with the Dresden Slate could one day benefit humanity. Although friendly toward military officers such as Daikaku Kokujōji, he opposed war and sought to distance himself from conflict, eventually retreating to the Himmelreich after what he believed to be the end of the world.

After inhabiting a new body and assuming the identity of Yashiro Isana, Weismann retained many of his core traits, including his charismatic, carefree, and kindhearted nature. Despite his amnesia, he adapted well to his new life by relying on intuition rather than dwelling on the past, often choosing to “follow his heart.” He is portrayed as laid-back, approachable, and able to form connections with nearly anyone, be it people, animals, or even machines. This openness allows others to trust him easily, though it also highlights his naivety, as he is willing to entrust his life to strangers.

Yashiro also demonstrates a mischievous or trickster-like streak, using humor and deception to mislead others when necessary. For instance, he once fabricated the existence of a younger sister to misdirect Kuroh Yatogami. Because of such antics, he has occasionally been regarded as insincere or dishonest.

He enjoys spending time in open, breezy places such as rooftops and bridges, and he expresses few dislikes. His favorite food is plain rice, and among his hobbies are research, joking, and eating.

During the final year of World War II, Adolf K. Weismann conducted experiments on the Dresden Slate in the city of Dresden. His research, which he carried out with his sister Klaudia Weismann, involved albino mice that reacted to the Slate’s power by generating potent Aura, some even manifesting their own Sword of Damocles. The experiments drew the attention of Japanese Lieutenant Daikaku Kokujōji, who proposed using the Slate’s power to create superhuman soldiers. Weismann opposed the idea, insisting that the Aura should be used to bring happiness rather than fuel warfare. Klaudia scolded him for speaking so openly in front of the Lieutenant, though the siblings laughed when Kokujōji admitted he understood little of their exchange.

Tragedy soon struck when Dresden was bombed, leaving the city in ruins. Amid the devastation, Weismann, his own Sword of Damocles visible above him, mournfully cradled Klaudia’s lifeless body. Though Kokujōji attempted to reach him, Weismann’s grief marked the beginning of his detachment from the world. By April of that year, he formally bid Kokujōji farewell, declaring that the war was over for him, and departed aboard the Himmelreich, a blimp that would become his sanctuary above the world.

Years later, Weismann was approached by the newly instated Colorless King. Initially cordial, their meeting quickly turned violent when the Colorless King incapacitated him. Weismann awoke to find himself displaced into a new body, clinging desperately to the edge of the Himmelreich while his original form now possessed by the Colorless King looked down on him. With a final act of betrayal, the Colorless King kicked him from the airship, sending him plummeting to Earth.

Weismann crashed through the roof of a gymnasium on Ashinaka High School’s island campus in Shizume City. Remarkably unscathed, he found himself face to face with a pink cat before being discovered by student Kukuri Yukizome. When questioned, he noticed a poster for the school festival and hastily introduced himself as Yashiro Isana, claiming to be a student of Ashinaka. Although Kukuri expressed doubt about his explanation, she accepted him as a classmate. From that point onward, Weismann now living as Yashiro came to believe in this fabricated identity, convinced that he was an ordinary high school student who had left his parents behind to study at Ashinaka.

Silver Aura
As the Silver King, Weismann wields the power of the Silver Aura, which grants him control over gravity manipulation. Through this ability, he can levitate himself or others whose Auras he has synchronized with. His status as the Silver King also bestows additional powers such as invulnerability and immortality.

Inviolability
A unique trait of the Silver King is inviolability, which renders him immune to external interference. This ability is demonstrated when Weismann survived being cast from the Himmelreich, suffering only temporary amnesia from the trauma of losing his body, and again when Kukuri Yukizome stabbed him, resulting in nothing more than a torn uniform. His original body also displayed this quality, remaining unscathed even after a massive explosion. In the manga, he is shown to easily nullify Mikoto Suoh’s flame attack.

Immortality
The Silver King possesses absolute immortality, rendering him incapable of dying, aging, falling ill, or sustaining permanent injury. His body and mind are completely self-sustaining, immune to physical, mental, or spiritual harm. Even when his body is seemingly destroyed, he regenerates without lasting damage, maintaining perfect health. However, he still experiences momentary pain when struck, as shown when he was stabbed, though the wound itself quickly vanished.

Intelligence
Weismann is noted for his exceptional intellect and memory, able to recall details from nearly a century earlier with total accuracy, including quotes read decades prior. A brilliant scientist and strategist, he and his sister Klaudia led groundbreaking research on the Dresden Slate. He also demonstrates a talent for deception, as seen when he outmaneuvered both Kuroh Yatogami and the Blue King, Reisi Munakata.

Tactical Genius
Shiro consistently proves himself to be an adept strategist, capable of formulating plans even when cornered. Examples include devising a ruse to trick Kuroh during their first meeting, manipulating Munakata into detaining “Adolf K. Weismann” as a distraction, and later orchestrating plans to destroy the Slate. He also coordinated an alliance between the Blue and Red Clans to combat the Green Clan, showcasing his ability to unite opposing factions against a common enemy.

Wagasa
Yashiro is often seen carrying a red wagasa (traditional Japanese umbrella) adorned with a distinctive four-pointed dark green flower outlined in gold near the ferrule. After losing his memories, he claimed the parasol had been given to him by his sister. The wagasa survived several battles, including being slightly damaged in the crater created by the Red King’s attack. During the assault on Mihashira Tower by the Green and Gray Kings, Yashiro even used it to deflect bullets fired by the Gray King, with no apparent harm to the parasol.

Himmelreich
The Himmelreich is the airship that Adolf Weismann retreated to following the death of his sister, Klaudia. It served as his sanctuary above the world until he was forcibly ejected from it by the Colorless King, who had taken over his original body. Later, the blimp was destroyed when the Colorless King set off explosives inside during Scepter 4’s attempt to bring it back to the ground, following Yashiro’s negotiations with Reisi Munakata, the Blue King.

Schattenreich
The Schattenreich is another airship, this one belonging to the Gold King, Daikaku Kokujōji. Yashiro was taken aboard following his final confrontation with the Red King, and it later became the site of Kokujōji’s death. After Yashiro’s body regenerated, he piloted the Schattenreich into battle, ultimately crashing it near the Yomito Gate during the assault on the Green Clan’s base, Jungle.