Miss Smith is dressed in a dark suit with dark glasses. This is a tribute to Agent Smith from Matrix (1999), who dressed the same way.
All the main monster girls are named after their respective species, with the exception of Papi the harpy.
Kimihito Kurusu's name is a pun, meaning "public host" ("kimihito" means "public", and "kurusu" means "host"), in keeping with his role as love interest/boarding companion for the monster girls.
Each girl has a different nickname for Kimihito, whose full name is only ever stated once, at the beginning of the series.
Miia refers to Kimihito as "Darling". This is a homage to the anime comedy Lamu (1981), whose lead female character Lum referred to her beloved the same way.