GrimGrimoire follows a young girl called Lillet Blan on her first few days at a prestigious yet mystical magic school. Having awoken on the fifth day to find everyone at the school has mysteriously vanished, she then finds herself returned right back to the first day of term with her memories intact. Now she has an opportunity to relive the past five days all over again and discover just what happened to the school's inhabitants and maybe prevent this terrible tragedy from happening all over again.