伊藤賢治
Kyoko Kishikawa has worked with Hirota on "Shadow Hearts", ' (although not ') and "Rogue Galaxy Premium Arrange", providing eerie female scat vocals for a number of his tracks. Ryo Fukuda has been the sound manipulator for Hirota on the "Shadow Hearts" games as well as composing and arranging a few tracks for all three games. He also co-composed with Hirota on "Sonic Shuffle". Kenji Ito worked with Hirota on the soundtrack of .