Mummy — In fiction mummies are undead creatures whose corpses has been mummified and animated. For more information on real life mummies and the process of mummification, read the related Wikipedia article.
Murder Mystery — This story has elements of crime fiction, mainly on the murder mystery front.
Muromachi Era — A game with this tag is set in Japan during the Muromachi era. The Muromachi era (also known as the Ashikaga era) is a division of Japanese history running from approximately 1337 to 1573.
Muscle Growth — This game features a hero and/or heroine that has a sudden increased in muscularity in a very short period of time. This is often the result of magic or some kind of drug.
Muscle Worship — Muscle Worship (sthenolagnia) is a mild form of BDSM where someone touches, rubs, massages, kisses, and/or licks the muscles of their partners body in a sexually arousing manner.
Musume-type Heroine — These games have at least one Musume-type heroine. These characters have no relation to the protagonist, like a blood-related-daughter or step-daughter, but they insist calling the protagonist as "father", "papa", "mom", etc. and acting like his/her daughter. For actual father/mother-daughter connections please use the daughter heroine tag.
Mutual Masturbation — A visual novel in this tag contains at least one scene of mutual masturbation. Mutual masturbation usually involves the manual stimulation of genitals by two or more people who stimulate themselves or one another. Types of mutual masturbation include the handjob and fingering. Stimulation of the genitals while using the feet may also be included, and so may manual stimulation of the anus.
My Little Pony — This visual novel features characters and/or settings from the My Little Pony franchise.
Mystery — Plot revolves around the solution of a a crime, secret, or unknown phenomena.
Mythical Setting — These tags are for games that feature scenes passing on locations taken directly from these myths (or locations inspired by those), not the games that has elements from these myths.
Mythology — Features mythical creatures, ancient gods, or other myths