Kuroki

Kuroki is the dignified butler who has served the Akiha household for over twenty years, looking after Rumiho since she was a child. His grey, slicked-back hair, bushy eyebrows, and ever-present black suit make him instantly recognizable.

He is a model of professionalism, able to slip out of a room without anyone noticing and single-handedly keep the sprawling Akiha residence spotless. Even he has his limits, though: certain especially chaotic guest rooms have proven too much even for him.

Kuroki is the one who greets Okabe, Itaru Hashida, and Mayuri Shiina whenever they visit Rumiho, doing it so quietly that Okabe later marvels at how the butler managed to vanish from the doorway without being seen. His surname, which literally means black tree, suits that same understated, almost invisible presence.