Yasushi Ishii (石井妥師, born March 10, 1970) is a Japanese composer, arranger, and musician from Utsunomiya, Tochigi Prefecture, Japan. Working across jazz fusion, experimental music, and hard rock, he debuted as a composer in 1991 after passing the EPIC/SONY FACE TO FACE AUDITION. He later worked with Takashi Utsunomiya, toured as a member of T.UTU with the BAND, and changed his professional name from 石井恭史 to 石井妥師. His music often uses dark, atmospheric textures that combine rock energy, electronics, and orchestral writing in action and supernatural titles, and he has released work through Epic Records Japan.
In 1994 he co-wrote songs with Takashi Utsunomiya under the name BOYO-BOZO for the T.UTU album "Water Dance", leading to the rock unit BOYO-BOZO, which debuted in May 1995 and was active only that year. In the summer of 1996, Ishii and Hidetoshi Nakamura formed 南烏山六丁目プロダクション and produced music for アニメ愛のあわあわアワー. He also worked under the name ACUPUNKTURE on commercial songs, returned to the BOYO-BOZO name for Takashi Utsunomiya's 2002 single "SING A SONG,miss clear light", and joined Takashi Utsunomiya's unit U_WAVE in 2005.
Ishii composed and scored the first Hellsing anime, and the music was released on two separate soundtracks; his work there helped define the series' intense, gothic mood. He also voiced the Intelligencer in the video game Chaos Legion. In anime song credits, he performed "Can you fly", the ED of "Darker than Black".
