Haruna, a fourth-generation Kongou-class Fog battlecruiser, operates through a humanoid Mental Model avatar. Tasked with enforcing the Fleet of Fog’s blockade against humanity, she confronts the submarine I-401 during an attack on Yokosuka Naval Base. Following her vessel’s destruction, Kirishima retrieves her core, leading to her Mental Model’s reactivation in an abandoned warehouse. There, Makie Osakabe—a child tied to the development of the Fog-countering vibration warhead—discovers her.

Haruna’s alliance shifts decisively upon bonding with Makie. Partnering with Kirishima, she safeguards the girl from military forces targeting her for the weapon’s secrets, abandoning Fog protocols by avoiding lethal tactics and enlisting the I-401 crew’s aid. Her defiance culminates in direct negotiations with Fog leadership, where she renounces her faction to prioritize Makie’s survival.

Integrating into the Blue Steel fleet, Haruna aids in transporting the vibration warhead to the United States while defending the group’s Iwo Jima base. Her interactions with Makie reveal an emerging grasp of human bonds, contrasting her prior role as an inflexible Fog enforcer. Strategic dialogues with Fog commanders further cement her break from collective objectives.

Her Mental Model’s appearance—a hooded coat concealing all but her eyes and nose—mirrors the Fog’s functional design philosophy while hinting at her developing individuality. Documented engagements across conflicts and command tiers trace her evolution from a rigid naval weapon to an autonomous guardian defined by loyalty to Makie and self-determined purpose.