(I don't own Danganronpa WITM, I just thought that this would be a fun scenario)
Monokuma has a new motive (don't question, he's done supernatural things in the past), each student slowly taking on the personality of another character that has some sort of relation to a deep secret they have (the source material being Alice in Wonderland characters, just for an example.) If a murder doesn't take place by the end of the week, their personalities would be totally overwritten, now let's see what anarchy unfolds because of this.