Karin Kuramae begins as a student at Tatsumiya Island's school, later becoming involved with the island's military organization, ALVIS. She appears in the prequel special, interacting with main characters like Ryo Masaoka and Yumi Ikoma. As Ryo's classmate, she learns he requires medication for inherited anemia and expresses concern for his well-being.

Her involvement deepens during the critical L-Plan diversion operation. Before Ryo deploys, he seeks someone to care for his dog, Pooky. After observing Karin successfully feed Pooky—notable as the dog typically only accepted food from Ryo—he entrusts Pooky to her care, alleviating his concern before the mission.

Following graduation, aware of ALVIS and the Festum threat, she formally joins the organization alongside other graduates, training as a pilot candidate for the experimental Titan-model Fafner units. After the L-Plan, she transitions to piloting the newer Nothung-model Fafner, specifically the Mark Zwei (II). Her combat deployment in the Mark Zwei is successful during an early engagement against the Festum on September 5, 2145, coinciding with the completion of the first two Nothung units.

Her story culminates during the initial Festum assault on Tatsumiya Island. While attempting to board her Fafner Mark Zwei unit to engage the enemy, she is intercepted and killed by Festum forces en route to the hangar, shortly before Kazuki Makabe deploys as a replacement pilot for the Mark Elf unit.