 According to an interview with developer Masato Kato, when deciding how to translate "Ryukenden" into English, the staff chose "Ninja Gaiden" "because it sounded cool".In Europe, the game was scheduled to be released in September 1990, but was delayed until September 1991.It was retitled as "Shadow Warriors"—just as "Teenage Mutant Ninja Turtles" was renamed "Teenage Mutant Hero Turtles"—as ninjas were considered a taboo subject in Europe.