Atsushi Kousaka is a Japanese voice actor born on February 22, 1985, in Nara Prefecture. He is affiliated with the talent agency AIR AGENCY. His journey into the voice acting profession began in his youth, inspired by watching dubbed foreign films with his family. He was particularly impressed by the work of Nachi Nozawa, the Japanese dubbing voice for Bruce Willis. He decided to pursue this career path around the age of thirteen. To fund his move to Tokyo and his education, he worked at a sushi restaurant while in high school, saving a significant sum of money. He is a graduate of the Amusement Media Academy in Osaka.

Kousaka made his debut as a voice actor in 2007, with his first credited role being a student character in the anime series CODE-E. In the early years of his career, he gained a variety of experience by voicing numerous supporting and background characters in a wide range of anime, including series such as Natsume's Book of Friends, Library War, and the reboot of the anime Katekyo Hitman Reborn!. A significant turning point in his career came in 2009 when he was cast in the popular web anime Hetalia: Axis Powers. In the Hetalia franchise, he has become known for voicing multiple characters, including the personifications of Prussia, Greece, and Estonia, roles he has reprised across several series and installments such as Hetalia: The World Twinkle and Hetalia: World Stars.

Since his debut, Kousaka has built an extensive and versatile filmography, lending his voice to a wide array of characters in anime, video games, and drama CDs. In anime, his roles span various genres and include the homeroom teacher in Talentless Nana, Eiji Arashiba in Scar on the Praeter, Lupitheon in Bakugan: Battle Planet, Daisen Kokuriki in Nanbaka, Tani in the film Doukyusei -Classmates-, and Osamu in The Asylum Session. He has also been a regular presence in long-running franchises, voicing numerous characters across multiple seasons of Duel Masters and various roles in the Future Avengers anime.

Beyond anime, Kousaka is active in the video game industry. His game credits include voicing Marco in Tales of Xillia 2, a character in Tales of Zestiria, and providing the Japanese voice for the superhero Hawkeye (Clint Barton) in the game Marvel's Avengers. He has also been involved in stage performances, radio programs, and narration work. His talents extend to performance direction as well; he served as the dialect director for an episode of the anime The Ice Guy and His Cool Female Colleague and performed the opening theme song for Scar on the Praeter. Known for his energetic spirit, he is affectionately called "Atsun" by his fans.