Iwai is notable for pushing new types of theme music in fighting games, going beyond the traditional "stage and ending" route to include personal winning themes (Darkstalkers), stage themes independent from character themes (Darkstalkers 3) and going so far as to replace every Street Fighter character's theme in Street Fighter Alpha 3. His music style more often than not falls under the heavy metal genre (especially for the Armored Warriors series) and is also notable for utilizing multiple thematic gimmicks (especially for the Darkstalkers series), the most recognizable perhaps being the "water drop."