Josh Emerson serves as an infantry soldier and scientific assistant to Martin Lazzari throughout the Godzilla anime trilogy. He joins the initial surface expedition to reclaim Earth from Godzilla. During reconnaissance, he observes flora resembling historical trees but receives Martin's warning against contact due to hazardous vegetation properties. He documents ruins of a former human city with the scouting team and survives a Servum ambush at the landing zone.

Following the catastrophic encounter with Godzilla Earth, he remains among the surviving human forces. He assists in deploying Mechagodzilla City's defenses against Godzilla Earth, evacuating when nanometal assimilation threatens Bilusaludo personnel and witnessing Godzilla Earth's annihilation of the city.

In the final conflict, he continues scientific duties with Martin Lazzari, monitoring Godzilla Earth's dormant state, unaware of King Ghidorah's destruction of the Aratrum. He observes the climactic battle between Godzilla Earth and King Ghidorah alongside Martin, Maina, and the Houtua tribe. After Godzilla Earth's victory, he embraces Houtua culture alongside fellow survivors, abandoning prior military objectives to integrate into their society.