Itsuki Sasara piloted the NES-2 Dolphin, a naval combat mecha capable of underwater and aerial movement, for the Neo International Defense Force (NIDF). This role distinguished her from fellow NIDF pilots who primarily operated the aerial-focused NES-1 Viper units.

A severe childhood accident necessitated life-saving cybernetic reconstruction performed by her father. This transformation into a cyborg granted her superhuman strength and agility. It also integrated a mechanical connection port into her right elbow, enabling a fluid interface with her NES Unit. Sasara deeply resented her cybernetic existence, preferring death, which caused significant estrangement from her father.

Her cybernetic enhancements and piloting expertise were vital to the NIDF's operations against the Hadean threat. She utilized the Dolphin's capabilities, including twin manipulator arms, VTOL flight, missile systems, and machine guns. No substantial character development or narrative evolution occurs across documented additional official media like OVAs, movies, or spin-offs.