Xexyz was originally released as Kame no Ongaeshi: Urashima Densetsu in Japan, which roughly translates as "Turtle's Gratitude: Legend of Urashima". Urashima is a character from Japanese folklore who was granted access to the underwater world after saving a turtle (the folklore-heavy Okami also references this story); a similar scene plays out in the intro cutscene to this game. In this sci-fi twist on the tale, the Urashima character is given a futuristic space suit and is tasked with saving a group of princesses across the cosmos from an evil force. Because the story of Urashima is largely unknown in the west, it was given the nonsensical title Xexyz and many of the Urashima references were scrapped, including the intro cutscene.
Xexyz spends its time in two modes: One is on foot, which plays like a Contra style run-and-gun and a second in the air which plays like a much more conventional shoot-'em-up. While on foot, the main character can enter doors in the background and find NPCs (and occasionally hidden bosses) that will provide extra story details or will sell stronger weapons and healing items in exchange for the game's "ball" currency. Each stage ends with a boss that needs to be fought in the shoot-'em-up phase. After which an additional shoot-'em-up stage carries the main character to the next world.