According to Akira Ushizawa in a 1998 interview published in volume 122 of Gamest magazine, he was asked where the idea of all of the game's fighters being summoned through a time machine to fight each other came from, and he responded:
"It was when we were first working on the planning, and thinking of stages for each character. We wanted those stages to have a lot of individual personality, and someone suggested the idea of setting the stages in different eras."
According to game's planner and director Kenji Sawatari in a 1998 Gamest magazine interview, he was asked why he added a female character to World Heroes. He responded:
"We haven’t had many female characters in our games up to now, so we wanted to add a proper one. Kagerou, the white ninja you can use after stage 3 in Ninja Combat, was ADK’s only other female character to date."