“Once, they carried zero atop their shoulders. Yet after losing their head, that has all come to naught.”
There’s a lot to decode in this cover page. Let’s start with the first and most obvious, the caption.
It’s a caption that clearly relates to Ui at least. Not only is Arima the leader which he aspired to be like whose now dead, but also Hairu herself died specifically by decapitation and losing her head. It is also quite literally that same head that brings Ui over to Furuta’s side and clouds his judgement. Saying “Ui lost his head” is not even symbolic by this point.