Jim Warston served as a maintenance mechanic in the Mars Base military, deployed with the ill-fated First Earth Recapture Force before the main events. This earlier invasion attempt ended in catastrophe, where Jim failed to save a close comrade from the Invid. Consumed by guilt over this perceived abandonment of duty, he deserted his post, labeling himself a coward.

After deserting, Jim lived within Invid-occupied Earth territory, actively avoiding direct conflict until encountering Stik Barnard and his freedom fighters. Despite profound self-doubt and reluctance to fight again, Jim joined their mission toward the Invid headquarters, Reflex Point. His technical expertise proved indispensable to the group, maintaining and repairing their transformable motorcycle-armors (MOSPEADA) and the transport vehicle Tread.

Throughout the mission, Jim frequently viewed himself as a liability due to past trauma and perceived cowardice. His companions consistently challenged this negative self-assessment, recognizing his courage and dependability during Invid encounters. His practical survival skills, mechanical resourcefulness, and steadfast loyalty gradually restored his sense of purpose and self-worth. Jim transitioned from a guilt-ridden deserter to a trusted, vital member of the resistance team.

Following the main conflict, as seen in the OVA "Love Live Alive," Jim remained with the group of survivors. He continued his role within the team dynamic, utilizing practical survival gear like sleeping bags during their travels, indicating his ongoing presence and integration into post-war rebuilding efforts.