Katsunori Okai is a Japanese voice actor from Hyogo Prefecture, affiliated with the talent agency Kenyu Office. He was born on October 8 and began his voice acting career in the 2000s after graduating from the talk back voice actor training school. He initially performed under the stage name "Katsunori Okai" written as 岡井克升, but officially changed his stage name to the phonetic rendering 岡井カツノリ in February 2016.

Okai has built a prolific career characterized by a high volume of supporting and guest roles in a wide array of anime television series. His voice can be heard in numerous popular and long-running shows. Among his earliest roles are appearances in series like the 2012 productions of Girls und Panzer and Sengoku Collection. In the years following, he accumulated credits in shows such as Active Raid, ALL OUT!!, and Drifters. A significant and recurring presence in his filmography is the long-running series Boruto: Naruto Next Generations, where he has voiced a multitude of different characters since 2017. He has also been a consistent presence in Ascendance of a Bookworm, playing various roles across its multiple seasons.

Beyond these recurring credits, his work includes the role of Toshi in the anime Bakugan Battle Planet, a character he also voiced in subsequent series like Bakugan: Armored Alliance and Bakugan: Evolutions. He also voiced the character Polke in Motto! Majime ni Fumajime Kaiketsu Zorori. His extensive list of television credits further includes major titles such as Spy x Family, Mobile Suit Gundam: The Witch from Mercury, Jujutsu Kaisen, Attack on Titan, My Hero Academia, and Detective Conan.

His career also extends to other media. In anime films, he has had roles in movies like Suzume and Detective Conan: The Black Iron Submarine. He is also highly active in video game voice work, with credits in major franchises including Final Fantasy VII Remake, the Yakuza franchise (as Nishida), Resident Evil 3 (as Murphy Seeker), and Armored Core VI: Fires of Rubicon. Additionally, he is frequently heard in Japanese dubs of foreign films and television series.

A key aspect of Okai's career is the recurring pattern of his collaborations. He is a regular voice in the Boruto and Ascendance of a Bookworm franchises, often providing voices for numerous distinct characters within each series. His body of work demonstrates a strong and ongoing relationship with the talent agency Kenyu Office. His notable achievements lie in his remarkable versatility and high volume of work, establishing him as a reliable and hardworking character actor in the industry. His ability to take on a wide range of roles, from background characters to named supporting parts across anime, video games, and dubbing, showcases his adaptability and solidifies his standing as a seasoned professional.