Alexandria Rivialle who is also known as 'The Shadow' in the Underground world because of her speed and being as silent as a shadow has been approached by Commander Erwin Smith to join the Military. After a hard time making a decision, she eventually enlists into the Military as Celestia Akeldama. What makes it interesting is that she is the sister of Humanity's Strongest. Having grown up with Levi Rivialle himself , it's not a surprise if this girl have a few tricks up her sleeve. Follow her as she trains with 104th Trainees Squad and eventually join the Survey Corp to meet her brother after 6 years. Will Levi eventually find out that his sister that he had left with an old lady named Maria Cromwell have eventually joined the military?