Description
Nils Nielsen, originally Nils Yajima through marriage, is a scientific prodigy who earned three PhD degrees in his youth, earning the moniker "Early Genius." His skills are influenced by his famous detective father and martial arts expert mother, shaping his tactical and investigative abilities. Representing America in the 7th Gunpla Battle World Championship with his Sengoku Astray Gundam, Nils participated chiefly to research Plavsky Particles, viewing battles as a method to access proprietary data from PPSE corporation founders. Initially detached, his perspective shifted profoundly after a pivotal match against Sei Iori and Reiji, where he discovered genuine enjoyment of the sport and recognized the emotional significance of Gunpla beyond mere utility.

Post-championship, Nils and his wife Caroline Yajima successfully recreated Plavsky Particles using collected data, achieving international acclaim. He retired from competitive fighting, believing his expertise granted an unfair advantage, and assumed the role of chief engineer at Nielsen Labs and Yajima Trading, focusing on developing Gunpla Battle systems. Seven years later in GM's Counterattack, Nils designs the large-scale battle system for Yajima Stadium and organizes an exhibition match, inviting former rivals Sei Iori, Meijin Kawaguchi, and Ricardo Fellini to test it. Though officially retired, he pilots the Ninpulse Gundam when the Gunpla Mafia hijacks the stadium, trapping attendees inside.

During the crisis, Nils demonstrates persistent analytical prowess and combat skill. He detects an optically camouflaged GM using the Ninpulse Gundam's sensors and destroys it, only to face waves of remotely controlled GM variants. He later teams with China Kousaka after her assistance, combining tactical acumen with her support. His actions aid the group in countering the Mafia's manipulations, including Plavsky Particle-based immobilization tactics. Nils's involvement underscores his enduring connection to Gunpla Battle, now fueled by camaraderie rather than research.

His relationship with Caroline evolved from reluctant interactions into a stable marriage; she assists his scientific endeavors and during the stadium incident. Post-crisis, Nils remains dedicated to advancing Gunpla technology through his engineering roles, cementing his legacy in the sport's infrastructure.