Here's the rundown from my point of view — I tore through the final chapters of 'Black Butler' and kept a notebook because I was that invested. The characters who clearly make it to the end are Ciel Phantomhive and Sebastian Michaelis — their bond, however twisted, remains central. Alongside them, the household staff (Finnian, Mey-Rin, and Bardroy) are shown alive and intact; Tanaka is also around, still grumpy but alive. Elizabeth Midford appears in good shape, and a handful of recurring side players like Lau and Ran-Mao show up without being killed off.
Some of the series' wilder personalities, like Grell Sutcliff and the Undertaker, also survive the finale in the sense that the manga doesn’t give them a clean death — they’re around, still doing their chaotic thing. A few villains get definitive ends, and others are left ambiguous, but the core Phantomhive circle survives long enough to close the book on their main threads. I closed the volume feeling satisfied and a little melancholy, like leaving a party at dawn.