The manga centers on the relationship between a middle school teacher who has a knack for gal games and a 14-year-old "perfect prospective wife" who is an expert on the Sengoku period. 

Koe de Oshigoto! is a story about Aoyagi Kanna, a 16 year-old girl who was asked to become an ero-ge seiyuu* on her 16th birthday by her 28 year-old sister at her ero-ge company. Can she do the job properly while she's still innocent and inexperienced? *Note: ero-ge seiyuu means erotic game voice actress.

The romantic comedy's story begins when the pretty, mild-mannered student council president announces a new dress code regulation, "underwear is now banned."