Haru got mindbroken from too much possessions, a deliberate punishment from Yuuko who felt Haru was no different from everyone else. Tsukishima went off the deep end on his own, developing a kinship and love for Yuuko. These feeling escalating when Yuuko getting her revenge just so happened to save MC. I have to assume Yuuko's spirit does move on, you can see her visage as Yagami dies, otherwise I don't know why she puts up with MC bullshit.