Yūjirō Someya has blue-grey hair styled in asymmetrical bangs and matching eyes. His height measures 157 cm initially, later reaching 161 cm. As an idol, his public image features a signature lipstick mark on his neck or left side during performances, often paired with a ribbon tie. Born into a kabuki theater heritage family, he is the stepson of renowned kabuki actor Tamagoro Someya. Yūjirō aspired to inherit this legacy but faced disinheritance after being judged insufficiently committed. This rejection led to prolonged isolation during early school years and deeply affected his self-worth. His stepbrother, Koichiro, initially disdained him due to his non-biological status and later inherited the kabuki position, creating tension. Over time, Koichiro comes to respect Yūjirō's idol career, while Yūjirō seeks to be seen as reliable by his brother. Privately, Yūjirō maintains an aloof, reserved demeanor contrasting his public "refreshing, kind, and cool" idol persona. He struggles to express emotions openly but harbors deep concern for those close to him, frequently showing protectiveness. Childhood loneliness and familial rejection fuel a persistent sense of inadequacy, driving him to overwork himself to prove his capabilities—a tendency causing multiple physical collapses. His stubbornness manifests in refusing to quit challenges, like enduring harsh treatment during a musical to demonstrate resilience. Outside idol work, he collects music CDs. His idol career begins when he independently auditions for a music competition. His performance alongside Aizo Shibasaki leads to forming the duo LIP×LIP. Initially, their off-stage relationship is contentious, marked by frequent arguments; Yūjirō perceives Aizo as loud and intrusive. Aizo's persistent efforts to include him gradually foster mutual respect, cemented when Aizo gifts him a prized stuffed animal. They establish a "secret spot" in a park for private conversations. Yūjirō grows fiercely protective of Aizo, confronting anyone who demeans him, and acknowledges Aizo as his unwavering support during emotional lows. Their dynamic matures into deep interdependence, though Yūjirō remains publicly dismissive of sentimental interpretations of their relationship. As Sakuragaoka High School classmates, Yūjirō and Hiyori Suzumi start with mutual hostility after she witnesses him being reprimanded at a police station. He frequently criticizes her "reckless" interventions and resents her initial ignorance of idol culture. Despite this friction, he assists her personal endeavors—helping her prepare for a meeting with childhood friend Nagisa Shiranami and encouraging her to accept Nagisa's feelings. He internally admires her determination to confront challenges without success guarantees. Their interactions remain combative yet underpinned by growing mutual regard. Yūjirō reconciles with his stepfather, who eventually supports his idol path, and improves his relationship with Koichiro through shared walks and conversations. During a solo Valentine's Day magazine interview, he admits lacking romantic experience and initially constructs his "ideal partner" around convenience. After observing Ken Shibasaki and Arisa Takamizawa's relationship, he revises his perspective to value open communication and mutual understanding, citing their dynamic as a model partnership. This highlights his gradual willingness to embrace vulnerability and acknowledge authentic connections.