Rei Miyajima serves in the EXOFRAME Force Recon unit. In 2016, he deployed to the Siachen Glacier via an exchange program with the Indian Army's Ladakh Scouts. His stated mission was to observe India's frontline deployment of armed Exoframes, technology restricted under the international Sankt Gallen Arrangement which Japan had signed. During this assignment, Captain Wangchuck demonstrated the ski-equipped Meghdoot Exoframe designed for mountain warfare, detailing its control via a consciousness-reading saddle and its speculated extraterrestrial biological origins beyond human reverse-engineering.

Miyajima engaged in a skirmish against Pakistani Gibraltar Exoframes that breached the ceasefire line. Combat actions triggered an avalanche. After disabling one enemy unit with his rifle, Miyajima pursued another on foot once the snow settled, discovering it abandoned and marked with a distinctive skull emblem featuring two red spots. Captain Wangchuck subsequently deduced Miyajima's false identity as a Japanese Self-Defense Forces observer. This conclusion arose from Miyajima's failure to recognize Rajio Taiso, a common Japanese calisthenics routine Wangchuck performed during the demonstration, which any authentic Japanese observer would have known.

By 2023, Miyajima operated with the EXOFRAME Force Recon team in Peru.