Seryu

Biodata

Feature	Value
Name	Seryu Ubiquitous (赛琉)
Alias(es)	Seryu
Gender	Female
Affiliation	Imperial Guard; later leaves the Imperial Capital with Koizumi and Chelsea
Occupation/Role	Imperial Guard member; later captain of the Imperial Guard
Equipment / Weapon	Teigu: Beast Transformation: Hekatonkheires, commonly called Koro
First Appearance	Chapter 9

Background / History

Seryu is an Imperial Guard member who patrols the Imperial Capital and declares that helping people in need is her duty under justice. During Reimu, Koizumi, and Hata no Kokoro's arrival in the city, she assists them and directs them toward shops. Reimu gives her a single-use amulet in return; it later blocks an ambush against Seryu. Grateful and curious about its non-Teigu properties, she visits the Hakurei Amulet Shop after patrol. 9

She promotes the amulet shop to colleagues and gives an amulet to her master, Ouka. Ouka overhears that the amulets work, suspects Reimu of ties to the Peaceful Path Sect, and blockades the shop. Seryu admits that she accidentally revealed Reimu's circumstances and apologizes to Koizumi, but remains caught between obeying Ouka and repaying the people who helped her. 16 17

Ouka's attempt to arrest Reimu and her companions makes Seryu feel increasingly estranged from him. She is visibly worried when he attacks Reimu and hesitates when ordered to use Koro against her friends. 17 18 Koizumi later considers her justice “twisted” by Ouka's influence, but believes her fundamental nature remains good. 24 46

After General Bude uncovers Ouka's crimes and removes him, Seryu's worldview collapses. Ouka had filled a parental role after her parents' deaths and shaped her understanding of justice. Bude promotes her to captain because she is a Teigu User, but she is disheartened by both Ouka's crimes and the discovery that many former Guard colleagues were corrupt. 43

Koizumi infiltrates the Guard base to find her. Although he is wanted, Seryu does not arrest him, choosing her own experience of his character over the Empire's orders. She accompanies him to Reias's mansion, where Reias's diary exposes the noble family's abuses. 47 48 49

Witnessing the mansion's massacre and discussing justice with Koizumi forces Seryu to confront the conflict between official duty and conscience. She concludes that justice concerns whether one's actions are worthy of one's own heart, then leaves the Imperial Capital with Koizumi and Chelsea rather than remain in the Guard. 50

Appearance

Seryu is described as a young woman with delicate cheeks. She is the sole woman stationed at the Imperial Guard base and is usually accompanied by Koro, which initially resembles a pet dog. 9 47 49

• Carries or remains close to Koro during patrols and duty. 9 47
• Her expression becomes notably subdued after Ouka's downfall and the Guard's restructuring. 43
• Koizumi lends her his black coat during a cold night outside Reias's mansion. 49

Personality

Seryu is enthusiastic, earnest, and strongly committed to helping others. She readily offers Koizumi assistance through the Imperial Guard and initially judges people through the information and orders available to her. 9 10 17

Her devotion to justice is sincere but easily manipulated. Ouka's teachings lead her toward an extreme and distorted approach, while her lack of independent information makes her vulnerable to superficial narratives—such as believing Night Raid to be evil solely from what she has been told. 24 46 50

Despite this naivety, she values gratitude and personal trust. She cannot bring herself to harm Reimu and Koizumi without evidence, regrets following Ouka's orders, and later refuses to arrest Koizumi despite his wanted status. 17 18 48

Following Ouka's exposure and Reias's crimes, Seryu becomes reflective and uncertain rather than blindly obedient. She seeks a definition of justice that can reconcile her conscience with her former role. 43 49 50

Abilities & Skills

Teigu: Beast Transformation: Hekatonkheires

Seryu possesses the biological Teigu Beast Transformation: Hekatonkheires, known as Koro. It can appear as a dog-like companion but transform into a giant, ferocious creature. 9 18 21 26

• Koro is powerful enough that Koizumi considers it beyond his ability to handle as an ordinary human. 21
• Ouka orders Seryu to use Koro against Reimu and Hata no Kokoro during the shop raid. 18
• Koizumi considers Koro troublesome because it can continuously regenerate. 48
• Koro remains alert beside Seryu and is meant to warn her of approaching intruders, though Koizumi evades it by concealing his aura. 47
• Its giant form requires feeding that Koizumi associates with human flesh, causing him to view the Teigu with disgust. 26

Imperial Guard Training

Seryu serves as a patrol officer and later becomes captain of the Imperial Guard after Ouka's removal. 9 43

• Handles disputes and public-order disturbances while on patrol. 10
• Leads Guard teams in Ouka's absence. 43
• Is regarded as diligent compared with corrupt Guard members. 43
• Respects senior Imperial Army personnel transferred into the Guard by General Bude. 43

Relationships

• Koizumi — Friend who worries that Ouka's influence will corrupt her; he infiltrates the Imperial Capital to find her, exposes Reias's crimes to her, and helps her reassess justice. Seryu trusts him over the wanted notice and leaves the city with him. 24 46 47 48 50
• Hakurei Reimu — Friend and benefactor. Reimu gives Seryu an amulet that saves her from an ambush; Seryu later feels guilty when her disclosure leads to the shop's blockade. 9 16 17
• Hata no Kokoro — Acquaintance through the Hakurei Amulet Shop and Koizumi's group; Seryu later says she wants to act with Reimu. 9 50
• Ouka — Former master and Imperial Guard captain. After Seryu's parents died, he acted as a parental figure and shaped her sense of justice; his proven crimes devastate her trust in him. 16 17 43
• General Bude — Takes control of the Imperial Guard, exposes and punishes Ouka and other corrupt members, and promotes Seryu to captain because she is a Teigu User. 43
• Chelsea — Accompanies Koizumi during the operation to retrieve Seryu and helps infiltrate Reias's mansion in animal forms. 47 48 50
• Koro — Her biological Teigu and constant companion, used for combat and alert duty. 9 47 48

Story Role / Major Arcs

Hakurei Amulet Shop Incident

Seryu's gratitude toward Reimu clashes with her duty after Ouka uses information she inadvertently revealed to accuse the shop of anti-Imperial activity. Her hesitation to deploy Koro against her friends foreshadows her break from Ouka's influence. 16 17 18

Ouka's Exposure and Guard Captaincy

General Bude discovers Ouka's crimes and restructures the Imperial Guard. Seryu becomes captain, but the revelation that her mentor and many colleagues were corrupt leaves her disillusioned and emotionally exhausted. 43

Reias Mansion and Departure

Koizumi finds Seryu at the Guard base and takes her to Reias's mansion to reveal the corruption she had unknowingly protected. After reading Reias's diary, witnessing the family's deaths, and debating the nature of justice, Seryu abandons the Imperial Guard and leaves the Imperial Capital with Koizumi and Chelsea. 47 48 49 50

Trivia

• Seryu is the only woman assigned to the Imperial Guard base; the base is reserved for her use while other Guard members live elsewhere. 47
• She initially mistakes Chelsea, disguised as a kitten, for an ordinary animal accompanying Koizumi. 47 49
• Seryu's refusal to arrest Koizumi is motivated partly by regret over having once prioritized Ouka's commands over her own judgment. 48