Inoue started boxing from a very young age, after watching his brother Naoya win several high school championships.
After a promising amateur career, he made his pro debut in 2013 as a light flyweight against future WBO minimumweight world champion Tatsuya Fukuhara.
Inoue then moved up to the flyweight division and faced Fahlan Sakkreerin Jr., winning the fight by unanimous decision.
After knocking out a debuting Chalerm Kotala, Inoue moved up to super flyweight and outclassed world title contender Nestor Daniel Narvaes.
Inoue defeated Mark Anthony Geraldo on July 6, 2015, to win the OPBF super flyweight title.
As the interim champion, Inoue became the mandatory challenger to the winner of the vacant WBC world title fight between Rau'shee Warren and Nordine Oubaali.
[10] Inoue made his first WBA bantamweight title defense against former IBF super flyweight champion Jerwin Ancajas.
Inoue defended his WBA bantamweight title against Seiya Tsutsumi at Ariake Arena in Tokyo, Japan on October 13, 2024.