Sebastian teaching a room full of rowdy schoolboys while Ciel investigates a conspiracy is the premise the series should have opened with. The animation team finally has permission to make this world look as gorgeous and menacing as it should, every shadow and butler gesture rendered with gothic precision. It's Black Butler remembering it's supposed to be fun, and that reminder lands harder than any of the heavier arcs.

Ciel Phantomhive accepts a royal commission from Queen Victoria: find one of her relatives who has vanished at Weston College, an exclusive boys academy known for its traditions. The young earl enrolls as a student while Sebastian, his demonic butler, takes a teaching post at the school. The missing person cannot be found anywhere on campus, and the headmaster, likely the only one with answers, cannot be reached. Only the four dormitory heads known as the Prefect 4 see him regularly, so Ciel sets out to win their favor and use their connections. Yet the college and its students keep far more hidden than he expects, and his mission grows harder at every turn.