Yajin Ro is a 15-year-old part-time worker of Chinese descent stationed on the moonbase, specializing in fine-tuning warship weapon systems, including those aboard the Queen Fuji. He displays a frequently sarcastic demeanor. His responsibilities expand to become the sole weapons officer on the Queen Fuji, where he skillfully operates beam cannons in combat, notably damaging the antagonist Golem by targeting a revealed weak point.

He develops a significant romantic interest in Nagisa Kasumi, one of the series' central figures. This attachment motivates actions such as confining Iczer-3 to the brig after she summons the Iczer-Robo during battle, an act he perceives as endangering Nagisa.

Official CD drama materials reveal his birthplace as Osaka, Japan, and highlight his culinary skills, developed through his parents' ownership of a renowned Chinese restaurant, demonstrated during a cooking competition with the character Atros. During the events of the "Iczelion" novelization, his romantic trajectory shifts as he enters a relationship with Kawai Shizuka, Nagisa's friend and coworker.