Lei Sai

Biodata

Feature	Information
Name	Lei Sai (雷赛)
Gender	Male
Affiliation	Demon Slayer Bureau; Qin Yuan's team
Occupation/Role	Third-Class Demon-Seeking Captain; archer, movement-technique specialist, and demon tracker
Cultivation	Early Condensing Qi Realm 62 168
First Appearance	Chapter 47

Power Progression

Chapter(s)	Development
62	Introduced as an early Condensing Qi Realm Third-Class Demon-Seeking Captain specializing in movement techniques, longbow use, topography, and demon tracking. 62
168	His early Condensing Qi cultivation is reaffirmed before the Blessed Land Grand Selection; his archery is acknowledged to require adequate distance and time to draw and nock arrows. 168
175	Participates in the fourth-tier division of the Blessed Land Grand Selection but is declared defeated following a rules violation. 175

Background / History

Before joining Qin Yuan's Demon Slayer Bureau team, Lei Sai pursued suspected demon activity involving a Pingwei Escort Agency convoy carrying Su Wanqing. He blocked the convoy after identifying a possible demon threat, but the escorts dismissed his suspicions and attempted to force him aside. 47 48 After Mu Yang killed the demon and struck Su Wanqing, Lei Sai questioned whether she should have been killed, beginning his recurring attempts to understand Mu Yang's uncompromising judgments. 49

Lei Sai was already a member of Qin Yuan's Demon Slayer Bureau team when Mu Yang and Ma Xuan were assigned to it. He recognized Mu Yang from their previous encounter with Su Wanqing's convoy. His bureau role combines movement techniques, longbow use, demon tracking, and a secondary knowledge of topography. 62

During the investigation of demon collusion in Wu Family Village, he and Mu Yang were tasked with collecting the informant Yue Miao. Lei Sai was troubled by the moral question of whether Yue Su deserved to die, while Mu Yang refused to entertain the dilemma. 63 He later participated in the investigation of Yue Miao alongside Mu Yang and Zhou Yao. 68

At Linhe Village, he supported Qin Yuan's team during the pursuit of a black-clad kidnapper and the appearance of the Drowned Corpse. He used his arrows to contain the black-clad man and employed the Demon-Seeking Compass to confirm that demonic energy was concentrated near the river. 108

After seeing Mu Yang defeat a Tier 5 Catfish Minion underwater without needing to breathe, Lei Sai was impressed and resolved to train harder. 113 However, Mu Yang's subsequent defeat of Bao Tian left Lei Sai and the rest of the team shocked and wary. 116

Following the Blessed Land Grand Selection, a clan marriage arrangement originally intended for Lei Jiaojiao and Mei Cao was redirected toward Lei Sai and a direct-descendant daughter of the Mei Family. His inability to oppose the arrangement caused Zhou Yao to avoid him and left him deeply despondent. 252 Mu Yang later accompanied him to the Lei Family estate, where the Lei Family patriarch agreed that Lei Sai should decide his own marriage. 253

Personality

Lei Sai is conscientious and prone to reflecting on difficult judgments, particularly when human wrongdoing and demon-related killings overlap. His tendency to dwell on such questions frustrates Mu Yang. 63

He is sociable with his teammates and maintains a friendly rivalry with Zhou Yao. 62 102 He admires Mu Yang's rapid progress, though it regularly leaves him incredulous. 102 125

Lei Sai is protective of Zhou Yao and becomes furious when Ji Bucheng deliberately humiliates her during the Blessed Land Grand Selection. 175 Despite his competitive spirit, he is self-conscious about his own talent and limited potential when compared with Mu Yang. 258

Around his family, Lei Sai is notably compliant with his sister Lei Jiaojiao and apprehensive of Lei Xing. 86 166 He wants to prove himself in the Blessed Land Grand Selection, but his early Condensing Qi cultivation and the practical demands of archery limit his confidence. 168

Abilities & Skills

Longbow Archery

Lei Sai specializes in the longbow as part of his Demon Slayer Bureau role. 62

• Demonstrated alertness and archery skill during the Linhe Village confrontation, where he held a black-clad opponent at bay with arrows. 108
• His effectiveness depends on having sufficient space and time to draw and nock arrows. 168

Movement Techniques

Lei Sai specializes in movement techniques. 62

• Uses mobility as a core part of his combat specialization.
• His early Condensing Qi cultivation is documented during the period before the Blessed Land Grand Selection. 168

Demon Tracking

Lei Sai excels at tracking demons. 62

• Carries and uses a Demon-Seeking Compass in the field.
• Used the compass at Linhe Village to identify demonic energy emanating from the river. 108

Topography

Lei Sai has secondary expertise in topography. 62

• Provides terrain-related specialization within Qin Yuan's team.
• Reflects the bureau principle that teammates cover one another's blind spots. 102

Relationships

• Mu Yang — Teammate and friend. Lei Sai first encountered Mu Yang while investigating Su Wanqing's escort convoy, then later served beside him in the Demon Slayer Bureau. He is repeatedly astonished by Mu Yang's advancement and combat strength; Mu Yang also intervenes to help him resolve his marriage dispute. 47 49 62 113 125 253
• Qin Yuan — Team leader in the Demon Slayer Bureau. 62
• Zhou Yao — Teammate, friendly rival, and romantic interest. They engage in playful banter and compete over their Blessed Land Grand Selection performances. Lei Sai is distressed when an arranged marriage causes her to avoid him, and later speaks openly of their hoped-for future child. 62 102 174 175 252 258
• Lei Jiaojiao — Sister. He is obedient to her wishes but becomes the target of her retaliatory “training,” including an enforced five-li underwater swim. She later feels guilty over the marriage arrangement imposed on him. 80 86 168 252
• Lei Xing — His great-aunt, the older sister of Lei Sai's grandfather and a powerful ancient demoness who appears as a little girl. She is the Water-Splitting Sect's Supreme Elder and a sixth-rank Aperture-Opening Realm martial artist. Lei Sai is hesitant to disclose her identity and is subjected to her harsh training. 166 168 191
• Mei Cao — Acquaintance and companion of Lei Sai and Lei Jiaojiao. Mei Cao's refusal of the planned marriage alliance with Lei Jiaojiao contributed to the arrangement being redirected toward Lei Sai. 80 86 252
• Lei Family Patriarch — Lei Sai's father, who initially upheld the arranged marriage but later permitted Lei Sai to decide his own marriage after Mu Yang's visit. 252 253

Story Role / Major Arcs

• Su Wanqing escort convoy incident — Pursues a suspected demon concealed within Su Wanqing's convoy, crosses paths with Mu Yang, and begins questioning Mu Yang's standards for judging demon collaborators. 47 49
• Demon Slayer Bureau recruitment — Introduced as a Third-Class Demon-Seeking Captain in Qin Yuan's team after Mu Yang joins the bureau. 62
• Wu Family Village investigation — Accompanies Mu Yang to retrieve Yue Miao and later investigates her apparent circumstances with Mu Yang and Zhou Yao. 63 68
• Linhe Village / Water Transport Gang case — Supports Qin Yuan's team at the river confrontation, uses the Demon-Seeking Compass to detect demonic energy, and later witnesses Mu Yang's underwater defeat of the Catfish Minion. 108 113
• Aftermath of Bao Tian's defeat — Is shaken by Mu Yang's overwhelming display of strength. 116
• Lei family training — After becoming drunk at Jixiang Restaurant, he is taken home by Mu Yang and forced into harsh river training by Lei Jiaojiao and Lei Xing. 168
• Blessed Land Grand Selection — Participates in the fourth-tier division, wagers competitively with Zhou Yao over who will last longer, and is later disqualified following a rules violation. 174 175
• Marriage dispute — Is assigned a political marriage with a Mei Family direct descendant, causing conflict with Zhou Yao, before Mu Yang helps secure the Lei Family patriarch's approval for Lei Sai to choose his own marriage. 252 253

Trivia

• Lei Sai drank the most during the Jixiang Restaurant gathering and was too intoxicated to return home unaided. 168
• His sister ordered him to swim five li underwater and return while holding his breath; failure meant he would not be allowed home. 168
• While enduring the training outside the city, he suffered an exceptionally terrifying nightmare. 168
• He repeatedly asks Mu Yang to explain difficult matters, only to be told to “figure it out” himself. 74 113 253