Hiroshi Nagahama was born on March 15, 1970, in Saiki, Oita Prefecture, Japan. He is an animator and animation director whose career began in 1990 when he joined the renowned studio Madhouse. His early work at the studio included in-between animation on series like Yawara! A Fashionable Judo Girl and the Record of Lodoss War OVA series. After leaving Madhouse, Nagahama transitioned to freelance work, which allowed him to take on a wider variety of creative roles. A significant early breakthrough came when he contributed to Revolutionary Girl Utena, where he was responsible for the series conceptual design, a role that involved creating the initial image boards for the show's distinctive forest setting, greenhouse, and student council tower.

Nagahama made his directorial debut with the critically acclaimed series Mushishi in 2005, a project he had long aspired to bring to the screen. He personally pitched the adaptation of Yuki Urushibara's manga to the publisher Kodansha, insisting it be his first work as a director. For his work on Mushishi, he received the 11th Animation Kobe Individual Award in 2006. Following this success, he directed other notable adaptations, including the vulgar heavy metal comedy Detroit Metal City and the controversial series The Flowers of Evil. For the latter, Nagahama insisted on using rotoscoping, a technique of animating over live-action footage, to capture the unsettling atmosphere of the source material, a method he acknowledged was expensive and risked negative audience reactions.

In 2017, Nagahama realized a lifelong dream when he co-created and directed The Reflection, his first original anime. The series was a collaboration with American comic book legend Stan Lee, a partnership that was deeply meaningful to Nagahama, who has been an avid fan of American superhero comics since childhood. He served as co-creator, director, and original character designer for the series, which was produced at Studio DEEN. The project was planned for worldwide distribution and represented a significant milestone in Nagahama's career, blending his expertise in Japanese animation with his passion for the aesthetic and narrative traditions of American comics.

Throughout his career, Nagahama has demonstrated a notable artistic flexibility, working across genres from fantasy and horror to comedy and psychological drama. Recurring themes in his work often explore the darkness hidden in everyday life, the transformation of the human body, and a sense of haunting beauty. His artistic identity is strongly influenced by his love of American comics and action figures, which he has cited as the starting point of his career as an animator. He has spoken about how the poseability and gimmicks of figures like Kenner's Super Powers Superman line influenced his thinking about movement and character design. This influence is evident in The Reflection, which was designed to have the visual texture of printed comic book paper.

Nagahama's industry significance is marked by his distinctive visual style and his willingness to experiment with unconventional production techniques. His use of rotoscoping in The Flowers of Evil and the decision to adapt Junji Ito's Uzumaki entirely in monochrome demonstrate a commitment to pushing the boundaries of the medium to achieve a specific artistic vision. For Uzumaki, a four-episode series released by Adult Swim in 2024, Nagahama directed the first episode. His approach to the project was shaped by his long-standing appreciation for horror, with films like Wicked City serving as a key inspiration for his career path. He has also worked as a series director on Jubei-chan 2 and as an episode director for anthology series like Rinshi!! Ekoda-chan.