In Mystic Messenger, the player takes the role of a female character whose name can be changed and has no default one. The female main character, who is often referred to as MC, heroine, or simply protagonist, downloaded a mysterious app that leads her into living in a closed, secured apartment owned by someone named Rika, who is also the founder of a charity organization known as the RFA (Rika's Fundraising Association). There, she meets 6 new people (the remaining members of the RFA) and is tasked to organize the third party that the RFA members have been longing for, by inviting guests. The protagonist is able to choose one out of 5 available love interests, each with their own route and backgrounds, as well as digging out the truth behind the RFA.