Koshi Inaba

Koshi Inaba is a Japanese singer, songwriter, and multi-instrumentalist who has spent over three decades as the vocalist and lyricist of B'z, the best-selling music act in Japanese history. With more than 100 million records sold worldwide, B'z have dominated the Oricon charts with 48 consecutive number-one singles and 27 number-one albums. Inaba's solo career has been equally formidable, six studio albums, all debuting at number one, and a string of collaborations with international rock figures like Slash and Stevie Salas.

What sets Inaba apart is the stark contrast between his explosive stage presence and his intensely private offstage life. He rarely gives interviews, keeps his family out of the spotlight, and lets his music do the talking. Fans know him as a vocal powerhouse with a four-octave range, a lyricist who blends poetic introspection with raw energy, and a mathematician who approaches songwriting like solving equations. As of 2026, he is still touring and recording with B'z, with a new solo album on the way.[edit]

Inaba grew up in Tsuyama, a small city in Okayama Prefecture, as the second of three sons. His father, a schoolteacher who later became a principal, kept a record collection that introduced young Koshi to The Beatles, Led Zeppelin, and Deep Purple. He picked up the guitar in elementary school and formed his first band in junior high, handling both vocals and guitar.

He was an exceptional student, especially in math and science, and after graduating from Tsuyama High School he moved to Tokyo to study at Yokohama National University. There he earned a degree in mathematics while playing in cover bands and writing original songs. The turning point came in 1987, when a mutual acquaintance introduced him to guitarist Tak Matsumoto. Matsumoto, already a well-known session musician, was searching for a vocalist for a new rock project. They clicked immediately, and B'z was born in 1988.[edit]

B'z broke through in 1990 with the single Taiyo no Komachi Angel, which launched a streak of hits that defined Japanese rock for the next decade. The 1998 compilation B'z The Best "Pleasure" sold over five million copies, and the duo's run of 48 consecutive number-one singles on the Oricon chart remains a Guinness World Record.

Inaba launched his solo career in 1997 with Magna, which debuted at number one. He followed it with five more chart-topping solo albums: Shiten (2002), Peace of Mind (2004), Hadou (2010), Tunnel (2021), and the collaborative Chubby Groove (2017) and Maximum Huavo (2020) with guitarist Stevie Salas under the name Inaba/Salas. In 2009, he sang on Slash's self-titled solo album, contributing the single Sahara.

In 2023, B'z were inducted into the Rock and Roll Hall of Fame with the Musical Excellence Award. The duo released Highway X in 2025, which debuted at number one in Japan. Inaba is currently working on his seventh solo album, expected in late 2026.[edit]

Inaba is known for his powerful, soulful voice and explosive stage presence, which contrasts sharply with his reserved, intellectual offstage persona. He is rarely seen in tabloids and gives very few interviews, which only adds to his mystique. His fashion is rock-oriented: leather jackets, band T-shirts, and sunglasses. Solo music tends to be more experimental and blues-based than B'z's hard rock, with introspective, poetic lyrics. Fans have no official name but are fiercely loyal; at concerts, they perform a syncopated "B'z clap" and wave light sticks in a specific pattern. Inaba himself has no personal social media accounts, but the official B'z channels are active and professional.[edit]

The loyal supporters of Koshi Inaba gather in massive numbers, filling arenas from Tokyo to Osaka with a singular focus on his live performances. Despite the sheer scale of their devotion, this collective lacks an official moniker, distinguishing them from idol groups with formal fan club names. They are simply the audience for one of Japan's most enduring rock voices, united by the raw power of his vocals and the intricate guitar work that defines his solo career. While B'z remains the best-selling act in Japanese history, Inaba's individual footprint is carved out through six consecutive number-one solo albums and high-profile collaborations with global rock icons like Slash. In the landscape of global celebrity metrics, Koshi Inaba stands as a figure of immense regional dominance but without a current placement in international tiered lists. iFANN has evaluated his standing, yet he does not currently hold a position within the Global Top 1,000 or any specific Top-100 scope list. This absence of a numeric rank reflects a unique trajectory where cultural saturation in one market does not always translate to a quantifiable score in broader global algorithms. The evaluation confirms his status as a legend within his domain while noting the lack of a formalized fandom name in available records. His influence is measured in sold-out stadiums and record-breaking sales rather than a specific digital ranking index.[edit]

Koshi Inaba brings an analytical precision to his art, holding a degree in mathematics from Yokohama National University that subtly shapes his songwriting structure. Beyond the stage, he is a licensed scuba diver and a devoted fan of the New England Patriots. His personal collection boasts over 200 vintage guitars, each chosen with the care of a curator. One of his most famous lyrical contributions, the lyrics for B'z's "Ultra Soul," were inspired after watching a documentary about sumo wrestlers. Yet, despite his commanding presence that often makes him appear fearless, he harbors a genuine fear of heights. Recent years have added new chapters to his legacy without creating old folklore. In February 2022, he collaborated with TK from Ling tosite sigure on the track "Scratch," blending distinct vocal styles. By November 2024, his intimate performance in the *Tiny Desk Concerts JAPAN* series showcased his versatility to a wider audience. A standout moment occurred during the 75th NHK Kohaku Uta Gassen in January 2025, where his explosive strategy captivated viewers nationwide. Most recently, in June 2026, he covered the classic anime theme "Touch" for Netflix's WBC support song, proving his ability to bridge generations of music fans.[edit]

Inaba is famously private about his personal life. He is married to a former model whose name he has never publicly disclosed. The couple has two children: a son born in 2000 and a daughter born in 2005. They maintain a low-profile life in Tokyo, with a vacation home in Hawaii. Inaba's father was a schoolteacher and principal; his mother was a homemaker. He has two brothers.[edit]

Inaba's primary collaborator is Tak Matsumoto, his bandmate in B'z and close friend. He has also worked extensively with American guitarist Stevie Salas under the Inaba/Salas project, and with Slash on the song Sahara. Longtime B'z producer Takuya Harada has been a key figure in shaping the duo's sound.[edit]

Inaba has kept his romantic life remarkably private. Before marriage, he was linked to a few women in the Japanese entertainment industry in the early 1990s, but none were confirmed as serious. In the mid-1990s, he dated a non-celebrity woman, though details are scarce. He married a former model in the late 1990s, whom he met through mutual friends. Her name has never been publicly disclosed. The couple had a son in 2000 and a daughter in 2005. As of 2026, they remain married, with no public record of any separation or divorce.[edit]

Per iFANN's editorial analysis, Koshi Inaba's net worth is estimated at $58 Million as of 2026. The foundation of this wealth rests on his dual role as lyricist and co-composer for B'z, an entity that has moved over 100 million records globally. Publishing rights and performance royalties from this vast catalog provide a consistent financial backbone. His solo endeavors further bolster his assets, with six studio albums all achieving number-one debuts and generating substantial revenue streams. Touring remains a primary income driver; both his solo circuits and B'z's stadium shows consistently rank among the highest-grossing events in Japan. Strategic endorsement partnerships with major instrument manufacturers like Yamaha and Gibson, alongside various fashion brands, add significant capital. Real estate holdings include a primary residence in Tokyo and a vacation property in Hawaii, rounding out a portfolio built on decades of musical excellence.[edit]

Inaba has won multiple Japan Gold Disc Awards for Best Male Artist and Best 5 Albums for his solo work, including Magna (1998), Shiten (2002), Hadou (2010), and Tunnel (2021). He also won MTV Video Music Awards Japan for Best Male Video (2003) and Best Rock Video (2005), and a Space Shower Music Award for Best Male Artist (2010).[edit]