The Japanese voice actor for the character Kimihiko Kimizuka in the anime series The Detective Is Already Dead is Arata Nagai. He was born on October 3, 1997, in Hyogo Prefecture. He is affiliated with the talent agency m&i. He had previously used the name reading Shin Nagai professionally but changed it to Arata Nagai upon joining m&i on January 1, 2021. Nagai is a graduate of the Mausu Promotion Actor Training Center.

His voice acting career began in 2015, and he has taken on roles in various television anime, games, and digital content. His appearance as Kimihiko Kimizuka in The Detective Is Already Dead in 2021 marked his first main character role and was a breakthrough in his career. Other television anime roles include appearances in Goblin Slayer, Shadows House, Active Raid, and ID-0.