Bersek used to serve in the Regular Army and was in a romantic relationship with Louise. He had planned for their engagement in the process. During an operation against an unknown enemy, Louise was wounded. Bersek hid her before going out to check their surroundings, despite her protests. He never returned, After regaining his will, Bersek holds resentment towards the Invaders for taking his life away and experimenting on them, wanting nothing more than revenge against his captors.