Random Theory Time: I think Yumi may have got
got.
So, the last time we see Yumi:
She is Tshaped in her pajamas.
Well, fast forward, and Sensei wakes up on a couch with blood behind him:
And what seems to be the edge of the shoulder of Yumi in her pajamas behind that couch:
Now, keep in mind, characters go invisible during the reset, so chances are, Maya and Ayane couldn't see Yumi's corpse. It's also been implied that Sensei needs to defile the girl first before he can see them:
So, I don't think Sensei could have seen her either, considering he hasn't really defiled Yumi yet. Also note how unlike whatever makes Sensei nude, Maya still had clothes on during the reset. Her PJs specifically, so, Yumi probably would have had hers as well.
We also had Sensei note something feels dangerous in Yumi's last event:
Then we saw this
twisted Ami thing:
At the end, seemingly staring at Yumi.
Overall: It seems like Yumi didn't make it to the roof, due to being murdered during the reset.