Hiroki Senō thrives as a competitive monobike racer and leader of the Killer Commandos in Aphrodia, Venus. His life revolves around high-speed racing within rollerball-style arenas until military conflict erupts. Witnessing Ishtar forces devastate Io, Aphrodia's capital, he initially avoids engagement. His perspective transforms upon discovering corrupt terraforming practices by Aphrodian officials, exposing systemic failures that worsened planetary instability.

Following the invasion, Hiroki joins an impulsive assault on an Ishtar tank at his former stadium, resulting in teammate casualties and their rescue by the Aphrodian Freedom Force resistance. Despite his aversion to warfare, Hiroki's unmatched monobike skills lead to forced recruitment into the Bloodhound Squadron. His relationship with resistance lieutenant Kurtz starts antagonistically, cemented by a grueling monobike race across lethal terrain proving Hiroki's raw talent. This compels a reluctant pact: Hiroki joins the squadron in exchange for his teammates' freedom.

Combat brings personal loss when teammate Will dies on a mission, intensifying Hiroki's drive. This coincides with journalist Susan Sommers' failed assassination attempt on Ishtar General Donner. In Io's decisive battle, Hiroki confronts Donner directly. Through tactical maneuvering, he provokes Donner into destructive fire that collapses a runway, killing the general and triggering Ishtar's occupation collapse. Post-battle, Kurtz gifts Hiroki his monobike as a gesture of respect, resolving their conflict. Hiroki later reunites with romantic interest Maggy at a refugee camp, guided by her cat Andrew.

Throughout, Hiroki exhibits rebellious defiance toward authority, including commanders and Maggy's bureaucrat father. His initial detachment from the political struggle evolves into committed participation, though motivations remain rooted in personal loyalties, not faction ideology. His actions reflect themes of individual agency amidst collective conflict.