Ichirou Inuyashiki is the central protagonist of his story, a fifty-eight-year-old salaryman who, at the start of the narrative, lives a life marked by quiet desperation. Despite his relatively young age, he appears much older, a condition attributed to a terminal illness and the immense stress of his daily existence. He holds a standard office job and has worked diligently to provide for his family, even saving money to buy a house outright, yet his efforts go completely unacknowledged by his wife and children. His family shows him little respect or affection, often treating him with open disdain or, perhaps worse, ignoring him entirely; his only consistent companion and source of comfort is his beloved dog, Hanako. After receiving the devastating news that he has advanced cancer and only a short time to live, he finds himself unable to share this burden with his uncaring family, leading him to a park where he breaks down in despair.

It is at this lowest point that an alien spacecraft crashes to Earth, accidentally killing him and a high school boy named Hiro Shishigami. To atone for his death, the extraterrestrials reconstruct Ichirou as a highly advanced, weaponized cyborg, transferring his consciousness into a completely synthetic and powerful robotic body. This transformation grants him incredible abilities, including superhuman strength, flight, durability that makes him impervious to conventional Earth weapons, the capacity to interface with any form of technology, and the power to fire devastating projectile weapons from his body.

In the face of this cosmic gift, Ichirou's fundamental personality shines through. He is a deeply compassionate and empathetic man who has always wanted to help others but was previously too weak and timid to make a difference. Where another person might use such lethal power for revenge or personal gain, Ichirou is terrified of losing his humanity and decides to use his new abilities to become a hero. His primary motivation is to prove to himself that he is still the man he was, and his actions are driven by a selfless desire to alleviate the suffering of others. He travels across the city healing the terminally ill, mending broken bones, saving people from accidents, and later defending entire populations from threats. Despite his mechanical body, which cannot digest food and has an altered sense of taste, his emotional core remains entirely human, demonstrated by his capacity for tears and profound feelings of joy and sorrow. Even his combat system has an auto-mode that reflects his moral code, acting to protect life when he is unconscious.

Ichirou's role in the story is defined by his stark opposition to Hiro, the other individual transformed by the aliens. While Ichirou saves lives, Hiro becomes a remorseless killer who murders for the thrill of feeling alive. This dynamic forces Ichirou into the position of an unlikely hero, the only being capable of confronting and stopping Hiro's rampages. His journey is intertwined with a small group of key relationships. His relationship with his family, particularly his daughter Mari, is a central arc; he begins as an ignored and pathetic figure, but through his heroic actions and a final, honest revelation of his true nature, he earns their love, respect, and tears. He also forms a partnership with a young man named Naoyuki Andou, who discovers his secret and becomes a crucial ally, helping him understand and train with his new powers.

Throughout the narrative, Ichirou undergoes significant development. He transitions from a passive, weak, and lonely old man into a brave and decisive figure capable of confronting overwhelming evil. His newfound power gives him the confidence he always lacked, but his core motivation remains grounded in compassion rather than a lust for strength. He finds a profound sense of purpose in being a savior, a stark contrast to the empty, meaningless existence he faced before his transformation. In the story's climax, his heroic journey concludes with the ultimate sacrifice. When a massive asteroid threatens to destroy all life on Earth, Ichirou flies into space to stop it. Despite his formidable arsenal being insufficient, he is joined by a repentant Hiro, and together they manage to alter the asteroid's course by detonating themselves, dying as heroes to save the world they both lived in.

Notable abilities granted by his mechanical body include a superlative healing power that can cure any illness or injury as long as the recipient is still alive, but he cannot resurrect the dead. For combat, his body contains numerous hidden mini-lasers and arm cannons capable of massive destruction, though he prefers using them with pinpoint precision, such as paralyzing a person by severing their spinal cord without killing them. He possesses full technokinesis, allowing him to wirelessly control any electronic device from any distance, from smartphones to airplanes. His flight capabilities are immense, allowing him to accelerate to escape velocity and operate unaided in the vacuum of space. Despite his power, he remains a fundamentally gentle soul who fights not because he enjoys it, but because it is the only way he knows to protect the preciousness of life he so nearly lost.