From 1990, Saito began collaborating with Hiroko Taniyama, arranging three songs on her album Tsumetai Mizu no Naka o Kimi to Aruiteiku.
In 1999, Saito began collaborating with singer Ringo Sheena, performing violins on her debut album Muzai Moratorium.
[2] In 2003, Saito arranged Sheena's song "La salle de bain", and in 2007 the pair worked together to create Heisei Fūzoku, a soundtrack album for the film Sakuran.
[5][6] Other than Taniyama and Sheena, Saito has collaborated with musicians Sayuri Ishikawa, Hikaru Utada, X Japan, Maaya Sakamoto, Seikima-II, Tamurapan, Radwimps and Yuki.
He was featured as violinist on the soundtrack for the anime Made in Abyss (2012–present), composed by Kevin Penkin, including the tracks "Hanazeve Caradhina" (2017), with over 5.5 million streams as of August 2023, "reBirth" (2020) and "VOH" (2022).