Toru Hoshina is a security officer in the United Nations Cosmo Navy who serves aboard the space battleship Yamato during its legendary voyage. Initially holding the rank of warrant officer, he is assigned to the ship’s security division under Lieutenant Shinya Itou. Hoshina presents a cheerful and supportive exterior, appearing as a friendly and trustworthy young man. However, beneath this amiable surface lies a sharp and capable intelligence operative. He is persistent, develops trust easily, and maintains a positive demeanor even in difficult situations, though he can be strict when necessary.

Hoshina’s core motivation is his sense of duty, which compels him to act in what he believes is the best interest of the Earth and the Yamato’s mission, even when it requires personal sacrifice and deception. His most significant early action occurs when a faction of the crew, led by his superior Itou, plans a mutiny to seize the Yamato for the Project Izumo resettlement plan. Unbeknownst to the mutineers, Hoshina had already been secretly recruited by Commander Heikuro Todo to infiltrate and stop any such activity. Hoshina plays a dangerous double agent role, gaining the confidence of the conspirators while working to ensure the mission continues. When the mutiny begins, he helps free loyal crew members, prepares the ailing Admiral Juzo Okita to resume command, and fires a single, non-lethal shot to disarm Itou, ending the uprising without bloodshed.

In his role aboard the Yamato, Hoshina is a dependable member of the security team, often tasked with observation and maintaining order. He develops a key relationship with Assistant Warrant Officer Yuria Misaki, initially approaching her with friendly persistence even when she is not particularly interested. When Misaki begins exhibiting strange behavior due to psychic control by an alien being, Hoshina becomes concerned and keeps a protective watch over her. During the Battle of the Rainbow Star Cluster, he leads her to safety and is wounded by enemy agents, an act that ultimately helps Misaki break free from her control. His steadfastness is rewarded, and by 2202, he and Misaki marry.

Over the course of the series, Hoshina’s character undergoes significant development. He matures from a young junior officer into a more seasoned adult. By the year 2205, he has been promoted to Lieutenant Junior Grade and serves as the head of security on the Yamato, taking on a mentorship role by keeping a watchful and understanding eye on the troubled new cadet Ryuusuke Domon. Later, he becomes the Head of Security for Earth Headquarters, tasked with investigating potential collaborators from the alien Dezariam empire. When Dezariam successfully invades and takes over Earth, Hoshina is forced underground, where he uses his intelligence and organizational skills to establish a resistance network against the invaders. While he is not at the forefront of combat, he is depicted as a highly capable strategist and operative who works effectively in the shadows without attracting attention. The narrative later emphasizes that he is not a superhuman but a talented individual who struggles, experiences defeat, and must persevere like anyone else. His notable abilities include his infiltration skills, loyalty, strategic thinking, and a talent for building trust with others, which serves him well both as a spy and as a leader of a resistance movement.