The player takes on the role of the MC (short for Main Character; can be also referred as Protagonist or Heroine), the main female protagonist of Mystic Messenger. After accidentally getting involved with the RFA, she takes on the job of former member and founder Rika to organize a party and invite guests.
During the process, she will be able to romance with one of the six main characters of the game throughout the eleven days of planning and conversing with the characters; depending on which route you're on.
Although there are five different standard avatars available for use in the game, the standard appearance of the MC is a slender woman with fair skin and brown hair with long bangs, as shown in several visuals of the game. Her eyes are not usually shown, but in the default in-game avatar, her eyes are shown to be amber.
Other options for the avatar include; a woman with pale skin, blue eyes and a blonde bob cut; a woman with green eyes and long, curly red hair; and woman with brown skin, golden eyes, and short, black hair with bangs. There is also a parodied version of the MC as a blue unicorn with pink hair. The player is also given the option to choose a picture from their files and make that their icon.
It is speculated that her eyes are never shown in the visuals so the player can imagine themselves actually being the MC, but some conversation shows that she is a "grown woman".
The MC's personality can differ slightly depending on which route is chosen. Overall, she shows compassion and kindness towards the RFA members. However, some of the options given can present the MC as selfish, usually leading to a bad ending.
Notably, she comes off as rather naive or too trusting, concerning how she seems to choose to trust Unknown/Ray's word at the beginning of every route despite how shady the situation is.
The MC's background can be whatever the player chooses it to be. The game usually assumes the MC is either a student, office worker, or someone who doesn't work and stays at home. At times the game will break the fourth wall and mention how limited the background options are.
The MC is a complete stranger to all of the characters at the start of the game. She downloads a suspicious app and is led to Rika's apartment by Unknown. When enters the apartment, she automatically connects to the RFA's chatroom on her phone. From that point on, she develops relationships with all of the other characters.
As Yoosung and MC become closer, Yoosung compares her to Rika to the point that it becomes an irritating tendency. After V comes to his apartment and apologizing, Yoosung moved on from Rika's death and becomes genuinely in love with MC. To protect the one he loves, he comes with Seven to the Mint Eye and encounter Unknown.
Zen is given a lead role in a musical stage thanks to the famous Echo Girl. As he becomes considerably close with MC, he hurt his ankle due to pushing himself too much, forcing him to turned down the role. When he realized that Echo Girl had another motive behind the role and rejected her, Echo Girl framed Zen with a scandal, stressing him out.
Jaehee becomes incredibly stressed due to the amount of work Jumin gives her. She develops interest in starting a café due to her love to coffee, but Jumin pushes her to keep doing the work he sets. There, both MC and Zen helping Jaehee overcome her trauma of not able to stand by her own if she's no longer with C&R International.
When Jumin is stressed by his arranged marriage, Jaehee sent MC and asked her to calm Jumin down. When Elizabeth 3rd gone missing, Jumin insisted that he's not a worthy owner and only needs MC. He even uses the hacker's danger as an excuse to keep MC from leaving the penthouse.
After once again hacking into the messenger, Unknown sends Jumin, Zen, Yoosung and Jaehee an email from Mint Eye, inviting them to their "party". This stabs Unknown in the back, as 707 is able to track down Mint Eye's address. Having no choice, Unknown travels to Rika's apartment to take the MC with him. 707 arrives in time and saves MC.
Unknown contacts MC 2 Years before the events of the Causal Story and Deep Story, telling her that he designed a game and wants her to test it for him. Unknown, now going by the name of Ray, picks her up and gives her a room at Mint Eye. Ray explains the RFA members are AI's he invented. She joins the RFA chat room and interrupts a conversation once again, this time V already being in the chat room. She joins the RFA by telling them Rika sent her as instructed by Ray. V joins Mint Eye in hopes of it leading him to Rika as he knows she didn't really commit suicide and in his stay in Mint Eye spots MC in Ray's garden and plans to get her out of this dangerous place, not before Ray and MC start a relationship of sorts and MC meets Rika. MC and V are then being held captive at Mint Eye and must get out before Rika harms V and Ray's obsession with MC gets out of hand.
Unknown sees her as a bait to make her enter Rika's apartment. He wants her to join the Mint Eye, but does not hesitate to kill her if she refused. In V's route he tends to be more gentle and softened towards her.
707 is the first person in RFA to see her face. After MC lives at Rika's apartment, he becomes the one who 'guards' her by monitoring the CCTVs placed around the building and in the hallways. At first, both of them love to share their jokes, to the point that they flirt with each other, although there some options where you can be mean to him. When they develop romantic feelings for each other, 707 refuses to admit his feelings as true due to his job and dark past. However eventually he opens up to her, allowing himself to be 'selfish' by wanting MC, even claiming that he isn't afraid to die for her.
Jumin will be respectful and friendly towards the player. Offering up to send her body guards when she's in trouble. Jumin and MC share a special kind of humor, one that the other characters don't understand, which Jumin is happy about. They're also very understanding of each other. Jumin isn't afraid of seeming obsessive over MC, to the point of even joking around about her going into his cage. In addition, Jumin wants MC to become more selfish and put herself first, before him. In the end, we can see just how much he cares for her, even when being surrounded by reporters and paparazzi.
Zen constantly flirts with MC shamelessly. Although he does, Zen is also possibly the most visibly showing person who generally cares for MC, to the point of putting himself in danger. In his eyes, MC is someone who understands him and sees his talent, rather than his looks, although MC isn't afraid to flatter his looks. From day 5 to 7 on his route, there are options where she can be mean to him but his feelings for her doesn't seem to waver and somehow acts like a masochist. He also treasures MC so much that he doesn't want to let his "beast" coming out until he can be 'responsible' for her. Due to his very romantic personality, he's not afraid to say how he feels about MC, although at certain times not allowing her say how she feels about him.
Yoosung, at first, sees MC as Rika's replacement due to him unable to move on from her death and that MC has the same job as Rika. However, he eventually realizes that the MC and Rika are very different from each other and he loves the MC as her own self, even growing into someone she can rely on.
As the only living female member of the group and someone who is stoic, Jaehee craves for a female friend. Even though at first she doesn't trust MC due to her sudden appearance and kept warning her about having romantic feelings towards Zen, they often fangirl together about Zen after they become closer. MC's support always gives her courage and the motivation she needed. Jaehee stated that MC is someone she treasures so much, as a "good friend". In the end, they become partners and opened a coffee shop together.
Due to V never being online for the majority of the time, he and the MC don't really have a lot of moments together but he truly cares for her as well as the whole RFA, as mentioned by Seven. V seems to have a sense of respect for the MC and hopes that they can become closer. In Zen's route day 10, he believes she is the chosen one so he asks her to take good care of the RFA members. Depending on the MC's choices around V, she also shares the mutual respect and trust for V or she is very suspicious of him.
MC is depicted as someone who was 'chosen' by Rika to take over her job. She's also initially compared a lot to Rika by Yoosung. Rika doesn't seem to mind that MC is used as bait to enter her apartment. In Another Story, Rika doesn't seem to show strong emotions towards MC at all, as she doesn't seem to be jealous or hate her, but doesn't show signs of caring or liking her either. However, in Another Story this changes, Rika is seen to have a very strong fascination with MC and grows to have love/hate feelings towards her.
- The first default avatar in the game features the design used in the game's CG.
- There are some case that when you choose a custom avatar, the picture will show up blank, as if there's limitation on file or resolution size.
- She has no default name, and you cannot proceed to the game if you leave them blank. There's no max number of characters to put in either, but the game will crash if her name is too long.
- Like other games with nameable heroines, other characters, if voiced, will refer to her as "you" in various forms of Korean.
- Several choices in the game allow MC to break the 4th wall.
- When Seven says "A visual novel gives you at least two options, but being a slave in money gives u one option," you may then respond with "This game isn't a visual novel, but it gives you more than two options."
- In a phone call, MC can ask Seven if he's going to "signing in to the mysterious messenger". He will respond with "are you mocking me that the messenger is hacked? T_T" which she will explains that it's a name of a game. Seven later told her to pursue the red haired character if there's one.
- In Zen's route, when Yoosung stated that he avoid on smoking cigarettes, MC can say she's thankful for Yoosung to keeping up with character setting, which responded with a confusion from Yoosung.
- In a day 1 chat, MC can choose to say "I still have no idea how to play this game T_T". After Jaehee is confused you may continue on to say "I just said it because it looked fun", which maddened her.
- During the Christmas event on (???) You can choose "You can't help but suspect something. After all this game's title is..."