Koji Seto's journey as an actor began when he was inspired by fellow Fukuoka-born actor Tsumabuki Satoshi's performance in the TV drama series "Orange Days". Seto was a student at the Fukuoka Actors School, a renowned institution that is part of the Himawari Acting School.
In 2005, he took on his first role in the TV drama "Rocket Boys" and subsequently won an audition for Watanabe Entertainment's acting group D-BOYS. The same year, at just 17 years old, he made the bold decision to move to Tokyo on his own.
Seto's early success led to a string of roles in TV, movie, and stage productions. His breakthrough year was 2008, when he became the first actor to appear in two leading parts, simultaneously, starring as Wataru Kurenai in "Kamen Rider Kiva" and Hiro in the TV drama adaptation of "Koizora".
The following years saw him take on a wide range of leading roles, including mentally disabled teenager Shuhei in "Rinne no Ame", a drama that won Fuji TV's 21st Best Young Screenwriter Award, and Yuta, the captain of a male-tumbling team, in the sport drama "Tumbling".
In 2011, Seto starred as the brave young Samurai Mori Ranmaru alongside Etsushi Toyokawa as Nobunaga Oda in NHK's Taiga Drama "Princess Go". The same year, he appeared in the TV drama "Rinne no Ame" and in the movie "Sadako 3D" as Takanori Ando.
In 2012, Director Shiota Akihiko chose Seto to star in the TV drama "Spy Tokku", a story about a spy who underwent a face transplantation when he started his job at the age of 19.
