Well Ave Mujica was pretty brutal for MutsuSakifags. Starts off with Sakiko not giving Mutsumi any kindness or support as she is breaking down. Then Sakiko ignores Mutsumi even after seeing a video of her fighting with Mortis to see her and she has to be forcefully dragged to Mutsumi's house.
Finally, we get a break with episode 7 with them making up. And episode 8 starts off well with Sakiko spending a lot of time with Mutsumi to make things up to her. Then the happy times end as it gets revealed that has had full on DID since she was a child. And this is the last time Sakiko and Mutsumi actually have a conversion for the rest of the anime.
Now Mutsumi and Sakiko get separated once more because Mutsumi "dies" again. And then Sakiko just gives up on Mutsumi completely. She doesn't bother to visit Mortis to try anything to get Mutsumi back. Instead she gets guilted into reforming Ave Mujica, drags Mortis out of bed and calls her Mutsumi accepting defeat.
Then we get zero reaction from Sakiko once Mutsumi starts playing for real during the live. And based on how she is walking back with Uika and what she said, she really didn't seem to notice the change. After this point all of Sakiko's focus goes to Hatsune.
So in the end there was a lot of suffering for little reward. Any happiness we got was quickly stripped away from us.