Ichirō Inuyashiki is a 58-year-old businessman who serves as the protagonist of the story. He is a middle-aged man who appears significantly older than his actual age, with a frail frame, gray hair, and a tired, aged face. At the outset, his life is defined by a profound sense of loneliness and quiet desperation. Despite working hard to provide for his family, including purchasing a new house with savings to avoid a loan, he is neglected and disrespected by his wife and children, who treat him with indifference and even contempt. He has no friends and finds his only companionship in a small stray dog he names Hanako. His already bleak existence is shattered when he receives a terminal diagnosis of stomach cancer, news that leaves him feeling utterly hopeless and invisible in his own home.

Inuyashiki's personality is initially defined by extreme timidity, introversion, and a lack of assertiveness. When confronted with cruelty, selfishness, or bullying, his instinct is to retreat into melancholy and cowardice. This meekness is a direct result of the emotional neglect he has suffered for years. However, this withdrawn exterior masks a deeply kind and empathetic core. He is not bitter or vengeful despite his miserable circumstances, but simply broken. This fundamental goodness becomes the driving force of his character after he undergoes a dramatic transformation. He does not seek power for its own sake but uses it as a means to connect with others and affirm his own humanity.

His role in the story is firmly established as a hero, though an unconventional one. After being accidentally killed by a crashing alien spacecraft, the aliens, in a rushed attempt to make amends, reconstruct his body into a highly sophisticated and powerful weapon-unit robot. His consciousness is transferred into a completely mechanical form that perfectly mimics a human外表. Upon discovering the immense power of his new body—including flight, superhuman strength, and advanced weaponry—he makes a conscious decision to dedicate himself to saving lives and helping the helpless. He uses his abilities to heal the terminally ill, rescue people from disasters, and stop acts of violence. His path inevitably places him in direct opposition to Hiro Shishigami, the teenager who was killed and rebuilt in the same incident but who chooses to use his powers for psychopathic murder and destruction. Inuyashiki serves as the emotional and moral counterweight to Hiro, representing the choice to do good even after being given godlike power.

Key relationships are central to Inuyashiki's emotional journey. His relationship with his family, particularly his daughter Mari, is initially distant and painful. Mari is ashamed of her father's pathetic appearance, but her perspective dramatically shifts when she secretly witnesses him using his powers to save people. This discovery forces her to reevaluate her father and eventually leads to a stronger, more understanding bond. He also forms a crucial friendship with Ando Naoyuki, a young friend of Mari who becomes Inuyashiki’s confidant and guide. Ando helps him understand and refine his new abilities, providing technical support and companionship without judgment. In contrast, his relationship with Hiro Shishigami is that of a direct antagonist, yet they are bound by their shared origin. They are two sides of the same coin, forcing each other into a final, inevitable confrontation.

The character's development is profound. He begins as a man on the verge of death, both literally from cancer and figuratively from a life devoid of meaning or affection. The transformation into a cyborg, which would be a dehumanizing event for many, paradoxically reawakens his humanity. Using his powers to save others gives him a sense of purpose and vitality that he had completely lost. He grows braver and more assertive, even standing up to his wife to defend Mari's dream of becoming a manga artist. He transitions from a passive victim of his life to an active force for good, finding that by helping others, he can once again feel alive. His advanced age and life experience provide him with a wisdom that prevents him from falling into despair or nihilism, even when faced with the immense cruelty of Hiro.

Inuyashiki possesses a vast array of notable abilities stemming from his alien-constructed robotic body. His body is incredibly durable, being nearly indestructible by any earthly weapon or force, and he possesses superhuman strength. He can fly at incredible speeds, using jetpacks on his back that allow him to travel faster than a bullet train and even fly into outer space. His sensory abilities are enhanced to a superhuman level, allowing him to see and hear across vast distances. One of his most significant powers is his ability to heal any damage, illness, or injury in living creatures, from cancer and broken bones to paralysis and burns, although he cannot resurrect the dead. He is also a master of technokinesis, able to wirelessly interface with, hack, and control any electronic device, from smartphones to missiles. For offensive purposes, his body is equipped with multiple weapon systems, including an arm cannon that can vaporize objects and numerous hidden lasers that can be fired with pinpoint precision from his back and shoulders to devastate large areas or perform delicate surgical strikes. While his body is mechanical, he retains the ability to eat and drink, though he cannot digest food, and his sense of taste is altered. A notable weakness is that he still feels pain with the same sensitivity as a human, and he requires water to function, becoming immobile if dehydrated.