Arajin Tomoshibi possesses fair skin, a slender build, jet-black hair parted down the middle, and reddish-brown eyes. He typically wears his school uniform jacket open over a red standing-collar shirt and purple tie, paired with white shoes. Early on, he is seen with grey half-rim glasses and carrying a bass guitar, though these are rarely present later. Casually, he favors outfits like a white collared shirt with a red sweater vest and baggy jeans. Personality-wise, Arajin actively avoids conflict and schoolyard battles, frequently escaping confrontations despite often finding himself in such situations. His primary focus is pursuing romantic interests, particularly developing an intense, immediate crush on Mahoro Jin after transferring to Ichizu High School. He exhibits over-expressive reactions around girls, often daydreaming about future relationships, contrasting with his underlying nervousness in social interactions. He tends toward self-absorption, prioritizing personal desires like losing his virginity over others' problems, and becomes evasive, shutting down when his past is referenced. Arajin moved back to his hometown with his mother after five years away, where they run the Chu Chu Chinese Restaurant. His father was absent early in life, possibly due to divorce or death. He reunites with childhood friend Matakara Asamine, with whom he once trained to become "Honki People." Flashbacks reveal Arajin was once a caring friend but distanced himself after failing to intervene when Matakara was bullied, adopting a cold and selfish demeanor as a coping mechanism. This history causes tension, as Matakara continues to idolize him while Arajin denies their friendship. Fleeing delinquents leads him to a shrine where he discovers an ancient revolver. Firing it, a bullet grazes his temple and embeds a metal bolt in his head, awakening the genie Senya. Offered a wish, Arajin surprises Senya by wishing to lose his virginity. This binds Senya to him, invisible to others unless they touch the bolt. Senya's influence enables Arajin to merge with him, granting supernatural combat abilities. Arajin is reluctantly drawn into conflicts between the Minato Kai and Siguma Squad gangs. After Marito Jin (Mahoro's brother) assaults him during a date with Mahoro, Arajin unconsciously merges with Senya to retaliate. This display makes him a recruitment target. He initially joins Siguma Squad due to Mahoro's manipulation—signaling him with a heart gesture—but later switches allegiance to the NG Boys when enticed by their showgirls. Character development occurs gradually. After repeated avoidance, he eventually confronts Matakara about his past cowardice, clarifying he isn't the strong figure Matakara remembers. By the series' conclusion, he rekindles their friendship, assuring Matakara he isn't alone. His motivations shift slightly; while still fixated on Mahoro, his final attempt to impress her involves adopting a style reminiscent of her brother, indicating consideration of her preferences. Crucially, he actively seeks fusion with Senya to rescue Matakara, demonstrating newfound resolve. A mysterious lotus-shaped tattoo above his buttocks appears, known only to Senya, though its significance remains unexplained. His hobbies include listening to music and playing bass, though his skill level is described as inadequate. Family dynamics highlight his occasional disrespect toward his mother despite helping at their restaurant, and his culinary skills in Chinese cuisine are noted as an inherited trait.