Hikozaemon Tokugawa is a veteran officer who serves as the chief engineer aboard the space battleship Yamato. He holds the rank of Lieutenant Commander and is a man of advanced age, described as being sixty-two years old, with a balding head and white hair and eyebrows that give him a distinctly middle-aged and seasoned appearance. His personal history is deeply rooted in the early conflicts of his world, as he served as the chief engineer on the battleship Kirishima, the flagship of the First Fleet. During this time, he worked under the command of Captain Juzo Okita during the inner-planetary conflicts that predated the larger interstellar war with the Garmillas Empire. This long period of service forged a powerful bond between Tokugawa and Okita, establishing them not only as trusted comrades but as the greatest of friends and mutual confidants. Despite originally being scheduled to retire from the military just two months after the Yamato was set to launch, Tokugawa agreed to postpone his retirement at Captain Okita's personal request to take on the crucial role of the Yamato's chief engineer. This decision underscores his sense of duty and his loyalty to his old friend.

Tokugawa's personality is defined by a gruff, no-nonsense dedication to his work and an unwavering sense of responsibility. He is a quintessential veteran engineer, possessing a deep, almost instinctive understanding of his vessel's machinery. His primary motivation stems from two powerful sources: his profound sense of duty to the ship and its crew, and his love for his family back on Earth. He has a grandchild, a granddaughter named Aiko, whom he adores and for whom he holds extremely deep affection. This connection to his family humanizes him, revealing a softer side beneath his tough exterior. During the Yamato's historic voyage, a poignant communication reveals his anguish as he learns that his son and granddaughter are suffering from severe food shortages on a devastated Earth, forcing them to rely on the black market for survival. This personal hardship, rather than distracting him, steels his resolve to see the mission through for the sake of his loved ones and all of humanity.

Within the story, Tokugawa's role is absolutely vital as the head of the Engineering Division. He commands a team of engineers, most notably his assistant, Susumu Yamazaki, with whom he shares a sincere bond of trust, and Sukeharu Yabu, an engineer he previously mentored on the Kirishima who views Tokugawa as his teacher. Tokugawa is responsible for the operation, maintenance, and repair of all of the Yamato's critical systems. His most significant responsibility is overseeing the ship's powerful wave motion engine, the vessel's revolutionary and most crucial piece of technology. In combat situations, he is responsible for damage control operations, though he often delegates the direct leadership of the damage control teams to Yamazaki while he focuses on the broader strategic overview of the engineering section's status.

Tokugawa's character development is marked more by a steadfast consistency than by dramatic change. He remains a rock of reliability throughout the journey. His most defining moment, and the tragic end of his character arc, comes during the climactic events of the second season. When a critical situation leads to the engine room becoming flooded with toxic fumes, Tokugawa is faced with a choice. Despite the mortal danger, he refuses to abandon his post, determined to remain at his station to keep the Yamato's vital systems operational. His dedication is absolute, and he ultimately suffocates in the engine room, sacrificing his life in the line of duty. This act of supreme self-sacrifice solidifies his legacy as being not just a skilled engineer, but a hero who gave his life for his ship and his crew. His notable abilities are not of a combat nature but are purely technical. He is a first-class engineer with decades of experience, and his expertise is a cornerstone of the Yamato's ability to complete its long and perilous voyage across the galaxy.