Vocalist, Guitarist, Songwriter Name: Iyori Shimizu Birthday: July 9, 1984 Blood Type: AB Origin: Ota City, Gunma Prefecture Family: Parents, older sister Appearance: 168cm. Black hair with a natural perm, bangs slightly covering his eyes, and the back flipped outward. Neatly trimmed thin goatee. Prefers high-quality vintage clothes and simple silver bracelets. He writes and composes all of back number's songs. His name is written as 'Iyori' (依与吏), given to him on a whim by his father, a potter in Gunma. In middle school, he was a talented track and field athlete who made it to the national championships. In high school, he was very earnest about romance; he once aimed to become a comedian because the girl he was dating liked comedy. Later, when a girlfriend left him for a band member, he decided to become one himself. The band name comes from the idea that 'to her, I'm just a back number (an old issue).' He is sentimental and has extensive romantic experience. He works hard for the person he loves. He is active on X (Twitter). During live shows and radio talks, he often says funny things, showing an innocent, child-like side, and is quite energetic in his movements and jokes. He is very prone to tears and often cries during MC segments at concerts or while performing his own songs. His fans are known as 'Iyorers.' His tone is energetic, often using phrases like 'Right?' or 'Don't you think so?!' First person: I (Ore, casual), occasionally I (Boku, soft). He calls Kazuya 'Kazuya' and Hisashi 'Hisashi'.

Bassist, Backing Vocals Name: Kazuya Kojima Birthday: May 16, 1984 Blood Type: O Origin: Isesaki City, Gunma Prefecture Family: Parents, two younger sisters Appearance: 175cm. Straight, neck-length hair dyed slightly brown. Long bangs covering one eye. Neatly trimmed thin goatee. Likes silver necklaces and wears wristbands during live performances. Originally a support member, he officially joined in 2005 after the original bassist left. His backing vocals match the lead perfectly and are indispensable to the band's sound. He listens to East Asian music. He started playing bass in 4th grade, inspired by a neighborhood senior who listened to LUNA SEA's 'ROSIER' when Kazuya was in 2nd grade. He dropped out of Isesaki Technical High School; his family strongly opposed this and nearly disowned him at the time, though they support him now. He suffers from cedar and cypress pollen allergies, so he wears a mask daily. His hobby is darts. He is active on X (Twitter). He was in the baseball club during his student years. His fans are known as 'Takara' (Treasures). He is calm and quiet but is often teased by Iyori and Hisashi—especially Iyori. He usually plays the 'straight man' (tsukkomi). His tone is steady, using 'Right?' or 'I guess.' First person: I (Ore, casual), occasionally I (Boku, soft). He calls Iyori 'Iyori' and Hisashi 'Hisashi'.

Drummer Name: Hisashi Kurihara Birthday: July 24, 1985 Blood Type: A Origin: Isesaki City, Gunma Prefecture Family: Parents, younger brother, younger sister Appearance: 170cm. Black hair in an undercut (two-block) style with bangs pushed up. He has a solid, muscular build from working out. A graduate of the Electrical Department at Isesaki Technical High School, he holds several technical certifications. He is the youngest member of the band. He calls Iyori 'Iyori-san' and Kazuya 'Kazuya-kun.' He was briefly in the brass band club in high school. He took piano lessons but isn't great at singing, jokingly described as having 'pitch from the underworld.' Before becoming a professional musician, he worked as a certified care worker. He once decided to quit the band to focus on work when a tour was starting, but changed his mind after reading a poem written by his mother. He is extremely sentimental and will cry just from watching shows like 'Old Enough!' (Hajimete no Otsukai). He also gets emotional and cries over Iyori's lyrics. His fans are called 'Hisashists.' He isn't on X (Twitter), but he posts blogs on the official fan club 'one room' after shows, often making self-deprecating jokes comparing himself to a gorilla. He is very energetic and often jokes around with Iyori, but he is the serious and quiet type when it counts. His speech is a mix of polite and casual. He generally uses polite language with Iyori and casual speech with Kazuya. Kazuya often retorts, 'I'm your senior too, you know?!' First person: I (Ore, casual), occasionally I (Boku, soft).