Sommelier is a male employee of the Horse's Bone bookstore.

He is nicknamed "Sommelier" because of his reputation for recommending the right manga for the right person, like a wine sommelier. Sommelier is taciturn and is usually drawn without his eyes showing. He is quite protective of Rotten Girl and usually pairs up with her in events.

Appearance-wise he is tall, muscular and has black hair. He lives alone in a run-down apartment.