This story is a sequel to Rebellion of the Moon

Something unbelievable had happened. Luna in her Nightmare Moon form is banished on the moon. She cannot believe it. But now regret fills her for Luna had lost her own sister. She is drowning in her own sorrow and doubt, which is placed by Nightmare Moon.
Celestia too struggles with the events. She is heartbroken for her own sister had betrayed her. But as the time goes by, Celestia tries to find out not what has happened, but why it had happened. For she has to know, what was her role in the tragedy of her sister. As if that is not enough, Celestia has to find a way, her nation can remember Nightmare Moon without denying Luna. But how can you remember a tragedy like this?