Yang Neumann is a sixteen-year-old engineer and hacker employed by Shinsei Industries as chief engineer for the experimental YF-19 Advanced Variable Fighter prototype during Project Super Nova. His technical brilliance and prodigious talent in variable fighter design secured him this significant role despite skepticism about his youth. His hacking expertise extends beyond aircraft; he repeatedly infiltrates the highly secured networks of virtual idol Sharon Apple, successfully stealing all her AI components except the non-existent emotions module. This fascination borders on obsession, influencing several of his actions.

His working relationship with YF-19 test pilot Isamu Alva Dyson is marked by mutual frustration, as Isamu frequently disregards protocols and damages the prototype through reckless flying, while Yang struggles to assert authority. Despite the tension, Yang correctly anticipates Isamu's decision to steal the YF-19 after Project Super Nova's cancellation due to the Ghost X-9 drone's selection. He convinces Isamu to take him along during the unauthorized flight to Earth. When Sharon Apple later takes over Macross City, Yang falls victim to her mass hypnotic influence and attempts to shoot Isamu mid-flight, though he misses. Isamu responds by ejecting Yang to ensure his survival.

In the Movie Edition, Yang's role during the Earth sequence includes additional context surrounding the confrontation with the hijacked Ghost X-9 and Sharon Apple's control over Macross City's systems. His technical knowledge remains instrumental in facilitating the YF-19's capabilities during this critical mission. His surname is noted as a probable homage to mathematician John von Neumann.