Homura Momiji is a character who first appears as a minor antagonist within Tsukasa Shishio's Empire of Might, later becoming affiliated with the Kingdom of Science. Her background reveals that before the worldwide petrification event, she was a highly accomplished professional gymnast, having even won the individual all-around championship at the All-Japan Championships when she was sixteen years old. She was originally from Fukuoka and was attending a training camp for designated强化选手 in Tokyo when she was petrified while practicing gymnastics.

In terms of personality, Homura is most notably characterized by her stoic and almost expressionless demeanor. She speaks in short, sparse sentences, often as if she is muttering to herself or thinking aloud, which contributes to her mysterious and distant air. Her most defining trait is her absolute and fanatical loyalty to Hyoga, a top warrior in Tsukasa's army and her immediate superior. She follows his orders without question, no matter how dangerous, ruthless, or morally compromising they may be, and has demonstrated a willingness to burn down villages and commit sabotage without hesitation. This loyalty is hinted to be rooted in a deep personal admiration, possibly even romantic feelings, that began before the石化, when she was mesmerized by his spearmanship. Despite her fearsome competence, Homura is not driven by her own ideology; she is almost entirely passive and predictable without Hyoga's directives.

Homura's primary motivations are intrinsically tied to Hyoga. Her actions throughout the story are almost exclusively performed to serve his goals and protect his interests. She is not motivated by Tsukasa's broader vision for a world of pure youth, but rather by her personal devotion to Hyoga as an individual. This is most clearly demonstrated when she follows Hyoga in betraying Tsukasa to sabotage the alliance between Tsukasa and Senku, carrying out the destruction of the Miracle Cave to prevent the mass production of the revival fluid. Her ultimate motivation is simply to serve and be near Hyoga, a fact that remains consistent even after her allegiances shift.

within the narrative, Homura serves as a key operative and elite spy for the antagonists. She acts as Hyoga's right hand and is deployed as a scout to surveil Ishigami Village and the Kingdom of Science. Her role is not that of a frontline powerhouse, but rather an infiltrator, saboteur, and information gatherer whose agility allows her to operate behind enemy lines with near impunity. A notable part of her role involves a long-term solo surveillance mission where she observes the village from the surrounding forest for months, memorizing the names and faces of all the villagers. Her significant actions include swimming unnoticed to set fire to Ishigami Village during a frontal assault and later destroying the vital Miracle Cave on Hyoga's orders.

Her key relationships are primarily defined by her connection to Hyoga, who is the absolute center of her world. She views him as her ideal and the only person worthy of her trust, and her loyalty to him is consistently prioritized over any other allegiance. She has a functional relationship with Tsukasa, obeying him only insofar as his orders align with Hyoga's. Her relationship with the Kingdom of Science, particularly Senku, is one of wary antagonism that develops into a reluctant alliance. Senku recognizes her skills and even suggests she is not beyond redemption, but his attempts to win her over are largely unsuccessful as her heart remains with Hyoga. She is captured by the Kingdom of Science on multiple occasions, using sophisticated tactics to finally overcome her speed and cunning.

Homura undergoes a significant but internal development over the course of the story. She debuts as a merciless antagonist, willing to burn a village with no regard for its inhabitants. After being captured and imprisoned, she has a period of forced reflection, during which small glimpses of her hidden emotions surface, such as when she suggests playing a word game with a captive Hyoga. Her most notable change occurs later when, following Hyoga's negotiation to join forces with the Kingdom of Science, she is revived from a petrified state as part of the deal. While she remains profoundly loyal to Hyoga, her role shifts from enemy combatant to an uneasy ally. She then works alongside the Kingdom of Science, participating in the construction of Corn City and assisting in the fight against the Stanley team in the North American arc, though her true allegiance remains with Hyoga alone.

Homura's notable abilities are almost entirely derived from her background as a professional gymnast. She possesses phenomenal speed and agility, allowing her to move with an acrobatic grace that can rival that of Kohaku, one of the strongest warriors in Ishigami Village. While she lacks raw physical strength, her exceptional technique and mobility, rated at the highest level, make her an incredibly difficult opponent to catch or pin down. Her combat style relies on evasion, repositioning, and using the environment to her advantage. Beyond her physical prowess, Homura is highly intelligent, observant, and cautious. She is a master of stealth and espionage, capable of remaining hidden for months and deducing the enemy's strategies from small details, such as predicting the movements of key individuals. She also possesses remarkable physical endurance, able to withstand long periods with minimal supplies, including free-diving at great depths and enduring winter conditions with only a simple cloak.