Alright! Finally some answers!
Looks like Shirley was weak from the start. The Shadows are actually just soot creatures like the soot monster from earlier (ghost?)
Ngl I find it super creepy how they just abduct children and then those soot fairies mimic them and finally they merge together...
Not your everyday yuri/shoujo-ai! As a lesbian I can tell you that I love this!! All of the pairs are different and lovely in their own unique way. Really refreshing manga with good characters! It deserves an anime adaption.