It was at this time that Ishii changed how he wrote his given name from (恭史) to (妥師), though the pronunciation stayed the same.
After Boyo-Bozo broke up, Ishii composed music for a number of other artists including Lazy Knack, Tomoe Shinohara, Masayuki Suzuki, and V6.
He also helped produce Naoto Kine's album Liquid Sun, Crystal Kay's first album C.L.L～Crystal Lover Light, and Daisuke Asakura's Siren's Melody single.
In 2012 both he and Hayato Matsuo composed the music for the short anime adaptation of Drifters, a manga series by Hellsing creator Kouta Hirano, this was included as part of the Hellsing: The Dawn OVA series showing up at the end of the final episode and lasting only 150 seconds, later on he composed music for the 2016 anime television series adaptation of Drifters.
He maintains a blog since 2007 where he shares new compositions on a monthly basis - some of which (SKY WALKER, BLUES OF FOREVER) are new renditions of songs from his work on Hellsing.