Kohaku Kongōji operates within the Science Division of the Gaist Crusher Garrison (GCG), a global entity focused on researching and combating metallic lifeforms called Gaist. She is the younger sister of Hayato Kongōji, a top GCG Academy graduate and primary wind-based Gaist Crusher. This lineage reflects a mineral-themed naming tradition: "Kongōji" incorporates "gold" (金剛), while her given name "Kohaku" means "Amber."

Her personality contrasts sharply with her brother's calm nature; Kohaku embodies the energetic Genki Girl archetype. She is the youngest and smallest member of the female operator trio, fitting the Token Mini-Moe role. A notable character trait is her intensely fierce, comedic reaction when insulted about her physical stature.

Physically, Kohaku possesses long brown hair reaching her hips and green eyes. Her typical attire includes boots and shorts. Although her primary role involves scientific support rather than frontline combat, her interactions include Ship Tease with Kurama Shindō, the earth-attribute Gaist Crusher and ninja clan heir.