A visual novel with this tag contains one or more scenes in which mouth gags are used in a sexual context.

A gag is usually an item or device designed to prevent speech, often as a restraint device to stop the subject from calling for help and keep its wearer quiet. This is usually done by blocking the mouth, partially or completely, or attempting to prevent the tongue, lips, or jaw from moving in the normal patterns of speech.

In BDSM, gags are usually associated with roleplays involving bondage, but that is not necessarily the case. The person who wears the gag is regarded as the submissive partner, while the other is regarded as the dominant one.