Weaksauce ending but I agree with scanlator that final twist saved it a little from being a complete letdown. Will try the author's other works to see if they are indeed better
Edit: Oh shait this is Marie no Kanaderu Ongaku author-- no wonder art seemed so familiar. I'll start from works...
It's nice how everything is coming together and all but this really would have been nicer with Sensei achieving his goal. Why you gotta make poor Satsuki a saint that has to save him