Hien, who also goes by her real name Naka, is a twenty-six-year-old female ninja from the Eastern Archipelago, specifically the island of Wa. She stands approximately 170 centimeters tall and serves as one of the personal retainers to Shuro, a young nobleman also known as Toshiro.

Born into a family of servants who have worked for Shuro's household for generations, Hien was trained as a ninja from a very young age, following in the footsteps of both her parents who also serve the family. She grew up alongside Shuro, taking on an older sister-like role to him when he was a young and somewhat timid child. As a result of this close upbringing, she once quietly assumed that Shuro might eventually fall in love with her, mirroring the relationship between his father and their senior retainer, Maizuru. However, she maintains that she never held genuine romantic feelings for him herself, though she was still surprised when he confessed his love for the foreign adventurer Falin Touden.

Hien possesses a highly confident and professional demeanor, grounded in her genuine skill and competence as a warrior. She handles nearly any task with ease and is acutely aware of her own abilities, which can make her appear somewhat arrogant or lacking in empathy toward others. She also holds a very high opinion of her own physical beauty, famously declaring that she does not wear makeup because doing so would make her even more beautiful and would only trouble the people around her. This unshakeable confidence, rather than alienating her peers, often disarms them. For instance, a blunt comment she made to her fellow retainer Benichidori about not needing makeup sparked a conflict, but Benichidori eventually came to appreciate Hien's honest and straightforward personality, and the two became close friends.

As a ninja, Hien is a highly capable warrior known for her exceptional agility and physical strength. She is incredibly acrobatic and light on her feet, once demonstrating her prowess by using the adventurer Kabru as a momentary foothold to launch a surprise attack on a giant sea serpent, throwing an explosive directly into its mouth. While she is an effective leader within the ninja unit under the command of the more senior Maizuru, she respects the hierarchy and follows her orders both on and off the battlefield.

Within her group of retainers, Hien often acts as a grounding presence. She frequently uses her practical comments to rein in the more fanciful ideas of her younger colleague Tade, though she also shows care for her when she is injured. She thinks less of another retainer, Asebi, whom she once scolded for a lack of gratitude toward the Nakamoto family.

During the expedition into the dungeon, Hien and the other retainers follow Shuro on his mission. She experiences a pivotal moment in the story when she is killed in battle against a chimerized version of Falin Touden, a shocking event that marks a significant turning point in the fight. She is later successfully revived by Maizuru's magic. Following her resurrection, she continues to serve her master loyally, and she is notably moved when Shuro, uncharacteristically, thanks his retainers and apologizes for the danger he has led them into.