The prior story is available here. The summary on this page contains spoilers about it.
Updated
Parts of this work are carried over from the setting of "Yumeyume Yumemiru Kotonakare" (2014/05/12).
The full story has been published, so please read it as well.
Summary
Finally captured by Reimu, Seija is forced upon the Myouren Temple.
She attaches herself to Nue, who worries that there is something strange about the "dreams", or nightmares, that Seija keeps having.
One day, Nazrin mistakes Seija for Ame-no-Sagume. Seija herself says "I kind of feel like I really was a goddess"...
Nue takes Seija to Satori, a contact from her time in the Underground.
Satori probes around Seija's subconscious and explains that her weak self can't bear the stress of the many legends and long history of 'the amanojaku'.
With Nue's help, Seija better understands her identity, stops having dreams and returns to normal. Her will for rebellion is renewed as well, and she leaves the Temple.