Based on the Phantasy Star Online 2 MMORPG published by SEGA. It covers the first three episodes of the original game and an original story. The game storyline follows members of a planetary exploration organization ARKS, based on the colony fleet Oracle that's searching for a habitable planet for its population. The members of ARKS defend Oracle and other planets from monsters called Darkers, which are under the control of the villainous Dark Falzes.
One day, the new rugby club member Akira gets advice on running from Riku, who used to be absorbed in rugby but gave it up because he lacked the physique for the sport. Akira takes an interest in Riku, and Riku's passion for the rugby gradually returns. By joining forces, the pair can play a new tactical game and aim for the top of high school rugby.