Yeah... I think the end-game isn't going to involve Nasa becoming like her- if anything, I currently think it's going to be the opposite: removing Tsukasa's heavily-implied immortality so she can live a normal human life, finally, with the man she loves. Because, to be honest, immortality is often treated as a curse in many cultures and works of fiction, especially for the good of heart.@TripleEm If she would have made him like her, then he never would have gotten sick.
Aya's moving on pretty quick. Hasn't it only been a couple months sense they got married in the story? Usually it takes someone longer to get over someone they loved...especially if they've loved them for years.