Vivienne, a newly constructed CAST android, and her partner (the player), discover that some SEED remain, and are causing trouble.

Vivienne and her partner work to save the Gurhal system—and, in the process, learn more about humanity.

The character design is adjustable through several variables: face model, eye color, eyebrows, eyelashes, ears, head type, body color, proportion, jacket, pants, shoes, voice type, and voice pitch.

Players are assigned missions in which they must kill all opponents in the area; many of the levels conclude with a boss battle.

[5] James Mielke of 1Up.com gave the game an A− stating, "The truly neat trick that Portable performs is that it is not only an excellent distillation of the Phantasy Star Online/Universe experience, but it makes me want to go back and give Ambition of the Illuminus another shot, even if it's just to reinvestigate that game's offline mode.