He joined Square in 1998 and his early work at the company primarily focused on sound effect design, rather than composition.

[3] He assisted Kenji Ito on sports video games such as Gekikuukan Pro Baseball: The End of the Century 1999.

[5][6] Along with Kenji Ito and Tsuyoshi Sekito, he created the soundtrack to Dawn of Mana (known as "Seiken Densetsu 4" in Japan), with Academy Award-winning composer Ryuichi Sakamoto providing the main theme.

He formed a rock band called The Primals with members of the sound team to play at Final Fantasy XIV events such as Fan Festival.

[2] Nobuo Uematsu's illness in 2018 prevented him from contributing the main theme to Shadowbringers as he had for every previous expansion;[14] Soken was tasked with the composition.

[16] For his work on Final Fantasy XVI, Soken and his team would be nominated and then win the Game Award for Best Score and Music in 2023.

[18] When tasked with arranging Final Fantasy music originally composed by Nobuo Uematsu, he takes extra care to achieve this goal.