Sick 13 Years (Attack on Titan)

After the death of Eren Jaeger due to his years being up and after the extinction of the Titans , Armin, Christa, Mikasa, and Annie move together to a beautiful small house by the ocean. But just when things were going alright, Armin gets incredibly sick, shortening his life span as a Titan Shifter. As the crew does their best to keep Armin alive, they also wonder why Annie was alive. Her time should have occurred a while ago. A mystery to be solved, but help was needed from someone smart... someone like Armin. And Christa loved Armin from the bottom of her heart (Sorry, I ship it) and she would do anything to keep him alive, but yet she was clueless of what she needed to do besides hope and pray. (THIS IS GOING TO BE A VERY SHORT STORY!! Also, my first story on Wattpad. Please cut me some slack, it might not be super good)