Yuuki Kaji is a renowned Japanese voice actor, singer, and actor born on September 3, 1985, in Tokyo, Japan, and raised in Saitama Prefecture. He is affiliated with the talent agency VIMS and the record label Lantis. Kaji began his path to becoming a voice actor after being inspired by the versatility of the profession during his中学 years. He graduated from the Japan Narration Acting Institute as a special scholarship student after being accepted into Arts Vision's free new talent audition.

Kaji's professional debut came in 2004 with a role in the PSP game "Teikoku Sensenki". His first role in an anime was a minor part in "Fushigiboshi no Futagohime" in 2006. His first leading role in an anime series came in 2007 as Mikoto Shinozaki in "Over Drive". A significant early role that brought him attention was as Finnian in the popular series "Black Butler" in 2008. That same year, he also played Akina Hiizumi in "Yozakura Quartet" and began co-hosting a radio show with Hiro Shimono.

Kaji's career is marked by an extensive and versatile portfolio of roles across a wide range of anime series. Some of his most iconic and leading performances include Eren Jaeger in "Attack on Titan", Shoto Todoroki in "My Hero Academia", Meliodas and his brother Zeldris in "The Seven Deadly Sins" franchise, Kenma Kozume in "Haikyu!!", and Nishikata in "Teasing Master Takagi-san". He has also voiced protagonists in numerous other hit series such as Haruyuki Arita in "Accel World", Shu Ouma in "Guilty Crown", Alibaba Saluja in "Magi", Issei Hyodo in "High School DxD", and Yukine in "Noragami". His filmography also includes significant roles in long-running and acclaimed series like Ryuichi Naruhodo in "Ace Attorney", Koichi Hirose in "JoJo's Bizarre Adventure: Diamond is Unbreakable", Speed-o'-Sound Sonic in "One Punch Man", Osamu Mikumo in "World Trigger", and Finnian in the "Black Butler" series. Kaji's talent extends to dubbing for foreign productions, such as providing the Japanese voice for the character Trent in "Kamen Rider: Dragon Knight".

Kaji's exceptional talent has been recognized with numerous prestigious awards throughout his career. He received the Best Rookie Actor Award at the 3rd Seiyu Awards in 2009. He then made history by winning the Best Lead Actor Award at the Seiyu Awards for two consecutive years, in 2013 and 2014. In 2013, he also won the Best Voice Actor Award at the Tokyo Anime Award and the Grand Prix in the voice actor category at the Animage Anime Grand Prix. He received the Yahoo! Japan Search Award in the voice actor category in 2019. More recently, he won the Best VA Performance (Japanese) award at the Crunchyroll Anime Awards in 2022 and 2023 for his role as Eren Jaeger in "Attack on Titan".

Beyond voice acting, Kaji has pursued a career as a singer, debuting with the single "sense of wonder" in 2012, for which he also wrote the lyrics. He has also taken on acting roles in live-action productions, including a lead role in the 2011 film "Kami Voice" and his first lead role in a television drama, "PIPLE: The AI Weds," in 2020. An author as well, he published a book titled "Itsuka subete ga kimi no chikara ni naru" (Someday Everything Will Become Your Strength) in 2018, which was later adapted into a manga. In 2024, he joined the "No More IA" initiative, a group of voice actors advocating against the unauthorized use of their voices by artificial intelligence, while also being involved in the development of officially licensed synthetic voice software. He has hosted various radio programs, including his long-running solo show "Yūki Kaji no Hitorigoto" (Kaji Yuuki's Monologue), which began in 2014.