I think 2-3 felt super disjointed to me for that exact reason.
The "Despair Disease" felt like a cop-out motive. If anything, Hiyoko should have been the main target, and Ibuki should have been caught in the crossfire, not the other way around. It was just such a weak fucking motive from the get go too. Like, most of the killings, as sadistic as Momokuma is, he tends to stay out of the actual murders themselves. But with 2-3, it felt like he was just like "lol, now ya'll have a disease that basically takes away your free will, lol have fun." It just feels so contrary to the rest of the motives, it takes away the tension, and really reduces the impact of Ibuki and Himiko's death's; they weren't killed because someone had it out for them, they were killed because "ohohoho, Mikan has "the Remembering disease", and now she's crazy!!!"
Fuck 2-3. The more I think about it, the more I'm pretty sure it's my least favorite chapter in the whole franchise so far.