D-9, a cyborg soldier introduced in the sequel *Return of the Overfiend*, displays formidable combat prowess by gunning down two Makemono demons assaulting his lover, Pedro. This establishes his protective instincts and lethal effectiveness. Following this introduction, his role diminishes to driving a tank transporting the main characters between locations. He undergoes minimal development, remaining a static figure until executing a heroic sacrifice. His compelling design and backstory hold unrealized potential, as his contributions to the overarching plot remain confined to his initial action and sacrificial conclusion. *(Note: D-9 does not appear in *Urotsukidōji II: Legend of the Demon Womb* and is exclusive to later sequels.)*