|“||I'm so glad we're hosting another party! I'm going to do better than last time so that Rika's not disappointed from up there.||”|
—Yoosung, Comment from RFA Orientation Guidebook
Yoosung is one of the Casual Story characters available in Mystic Messenger. Yoosung is a sophomore college student who plays a game called LOLOL and invests too much time into it. Because of that, he does not spend as much time studying for college and neglects his studies. Yoosung is also the cousin of Rika and cannot fully bring himself to believe that she is not alive anymore.
Yoosung is a really nice and lovable person, and is described by the other RFA members as 'a real puppy'. Yoosung cares about people a lot and loves to spend time with others. He is naive and believes things that are told to him more often than not, as shown during several of his interactions with 707. As a result, he is often unforgiving to his naive nature.
Despite his somewhat naive and lighthearted nature, Yoosung is severely depressed after the death of his cousin, Rika, with whom he had a very close relationship with and who he idolized. After the death of Rika, Yoosung lost all interest in his studies and becomes a shut in, rarely leaving for classes and opting instead to play LOLOL in order to cope with the crippling sadness.
During Yoosung's route, 707 states in a phone call with the MC that Yoosung had yandere tenancies, which the MC can expand on if she wants. This reveals Yoosung to be a very possessive person, asking the MC to only text him, to only call and talk to him. The MC can expand on his yandere tenancies which will result in a Bad Ending if she also encourages him to see her as a new Rika.
He is the shortest out of all the male characters, at 171 cm (5'6") and is also the most youthful appearance and age-wise. He has messy, bleached blond hair that he usually keeps out of his eyes with two dark brown hair clips that form an 'X' shape. He has soft violet eyes and a young aura to him in all his photos. His style of clothing usually contains something blue.
It is stated that Yoosung dyed his hair blond in order to get a girlfriend, but also to perhaps look closer in appearance with his cousin who was also blonde. His natural hair colour is a dark brown was usually well kept. Before Rika's death, it is shown in photos that Yoosung would wear more formal clothes before he went to college.
Yoosung grew up in what he calls a typically normal family with his mother, father and sister. It wasn't until the 6th grade that Yoosung met his adoptive cousin, Rika, and began to spend more time with her at his mother's behest.
Eventually, Yoosung began to greatly admire and idolize Rika for her kindness and ability to make others happy; Yoosung admits that he even thought of Rika as a "magician" who could bring happiness to everyone. As a result of his close friendship with his cousin, Yoosung eventually joined the RFA and became friends with the other members.
Rika was a big influence on Yoosung and he decided to apply to SKY University as she had told him to instead of applying to a college closer to him. It was because of Rika that Yoosung decided to become a vet after the death of her beloved Sally, who she loved so greatly.
Rika had a great hand in shaping Yoosung and his future, making him want to become better and to achieve better results in classes and was the reason he wanted to score top results. Her death shook him so greatly that Yoosung states it was a few days before the realization hit him and the tears wouldn't stop coming. After her death, Yoosung became closed off and unmotivated in life, seeing no point in continuing his studies and finding it difficult to cope with the sadness he felt at her death. Eventually, he discovered LOLOL and used it as a means to escape from his depression, neglecting his studies.
When the MC first enters the group chat, Yoosung is initially wary like the other members but is more trusting of the MC. He immediately attempts to be friends with the MC and begins to ask her about her life, before stating that he
believes that the MC is like Rika, his cousin who he had lost two years prior to the story. Yoosung shows himself to be the victim of 707's pranks, which the MC can play along with or try to stop 707's teasing of the younger boy, the latter resulting in obtaining more hearts from Yoosung. The MC shows interest towards Yoosung's hobbies, such as gaming, and can agree that V is suspicious, which will result in them growing closer.
If the MC manages to obtain Yoosung, the two will instantly enter into a very close and cute relationship; out of all the members, Yoosung is the one who calls the most during his route, with nearly after every chat you have with him. Yoosung will almost instantly tell the player his feelings and the two will become a "cutesy" type couple, but it will be a while before Yoosung will ask the MC to be his girlfriend.
During the route, the MC can choose to either encourage Yoosung to drop his studies and that he only needs her, or she can gently support him to give up gaming and to start focusing on his studies. The other members note how much Yoosung has changed in such a short time thanks to MC and her support, but are concerned at how quickly the relationship is progressing. However, it a problem occurs when Yoosung begins to continuously compare the MC to Rika, saying that she shares many traits as her and even going so far as to say that she's "basically" Rika; such an example is when he sends a picture of Rika's dog Sally and, if the MC asks if that is Sally, says that he knew she would "recognize" the dog.
This causes the other members to become concerned for Yoosung and the MC can either encourage Yoosung to think of her as Rika or tell him that while she's grateful that he thinks highly of her, she is not Rika. Encouraging Yoosung to think of her as Rika, will lead to Yoosung to become more possessive and controlling, his "yandere" tenancies coming forth. If the player acts controlling and equally possessive of Yoosung, a Bad Ending will occur when Yoosung steals the address for Rika's apartment to go to the MC; he is initially brought back to sense when he sees that the MC looks nothing like Rika but returns to his "yandere" self and the secret bomb placed within the apartment detonates, killing the two instantly.
If the MC remains supportive and understanding of Yoosung, he eventually realizes that the MC is not Rika, despite the similarities, and that he didn't understand that it was wrong to compare since he thinks both the MC and Rika are amazing people, but will see the MC for who she is, not who she reminds him of. The two enter a brief moment of peace before 707 enters the chatroom to tell the RFA that he had found traces of the hacker during the past few days and that he had managed to change the algorithm of the secret bomb placed in Rika's apartment at her request; if any member tries to enter, of if the MC attempts to leave, the bomb will most likely detonate.
This leaves all the members in a state of shock and disbelief at the fact Rika had requested a bomb be placed in her home and the fact that V knew and allowed the MC to stay there; Yoosung is immediately alarmed and worried for the safety of the MC, becoming distrustful of the RFA and even more hateful towards V. The MC can agree with Yoosung that the RFA can't be trusted, or attempt to calm him down and broker peace between Yoosung and the other members; Yoosung becomes depressed at the prospect of losing the MC as he lost Rika and is furious towards V, who he believes if responsible for Rika's death This anger remains even when 707 recovers the special security system and refuses to give the apartment's address or let the MC leave.
After Yoosung becomes emotionally distant, V visits him suddenly in hopes of cheering him up and to promise that the MC is safe; Yoosung is furious with V and blames him for the death of Rika, saying it was his fault that she died and that he hates him. He blames V and says it is all his fault, for Rika, for putting the MC in danger, and V accepts the blame. In a moment of rare truth, V tells Yoosung that Rika was suffering from mental health issues and had refused treatment for them, and became increasingly unstable before she finally committed suicide. The shock shakes Yoosung and only then does he see V's condition. With his faith in V and the RFA restored, Yoosung visits Jumin and asks him to send more bodyguards to protect the MC and to ask V to receive treatment for him blindness one last time; Jumin complies, but only if Yoosung agrees to take care of a stray kitten he found some time prior.
Despite this, the situation slowly deteriorates within the RFA; Zen is harassed by a stalker outside of his house, and Jaehee receives a suspicious email from Mint Eye. Seven traces the e-mail back to its original location, and decides to go investigate. Wanting to protect the player, Yoosung volunteers to come as well. Before they leave, Yoosung shares one last chat with the MC, talking to her about her likes her for her and not because she reminds him of Rika; it is then he asks the MC to be his "pre-girlfriend", and if they can start officially dating after they deal with the situation with the hacker.
707 and Yoosung arrive at Mint Eye's base and find it be void of people; 707 attempts to recover whatever data that may be left behind and has Yoosung stand guard; there, he has a chance encounter with the hacker, Unknown, and he tells Yoosung to leave so that he can talk to him by himself. It is revealed that 707 recognises the hacker and is clearly flustered by him, becoming ensnared by the hackers words as Unknown attempts to get him to detonate the bomb in Mint Eye and in the apartment. Before 707 can press the button, Yoosung appears and struggles with the hacker, telling 707 to run with the detonator.
The two attempt to run but Yoosung is caught by the hacker without 707's notice and it isn't until later that 707 notices. By then, it's too late and the hacker has gravely injured Yoosung. V arrives in time and manages to save Yoosung and 707 from the hacker, bringing Yoosung to the hospital to get him treated. Not wanting the MC and the others to worry, Yoosung lies about being alright and that the mission went well. It isn't until later at the hospital that it is revealed Yoosung has lost sight in his left eye thanks to the hacker, but it otherwise unharmed.
The other members arrive at the party and find that Yoosung will be arriving with V, much to their surprise. They are unaware of the situation until 707 breaks down in front of the MC and tells her the truth about what happened. The others are shocked and Jumin and Zen decide to head to the hospital before the others notice that Yoosung has arrived at the party, the left side of his face completely bandaged after being released from the hospital.
He makes a speech to the party guests, talking about how much he admired his cousin Rika and the other members of the RFA before confessing his love for the MC, saying that he was glad to have sacrificed himself for her safety. The two then share a kiss in front of the other guests and members, with Yoosung saying he has longed to see her and it's okay now, since she isn't Rika.
Yoosung is quite close with Seven. He often falls for the jokes/pranks Seven plays on him and is incredibly gullible. Seven was unable to make it to Yoosung's high school graduation due to being abroad at the time.
Yoosung was the closest to Rika, being her cousin and all. They had a very close relationship and when she "passed away", Yoosung was devastated and became very depressed.
Yoosung distrusts V and even goes as far as to hate him. Yoosung thinks that V changed after Rika's death and is upset that V couldn't give more evidence about her death, but in the end 'forgave' him after moving on with Rika's death.
Yoosung is close with Zen, and he is jealous of Zen's good looks. Zen acts like an older brother towards Yoosung. Zen congratulates Yoosung on his relationship with the player, but warns Yoosung not to compare Rika to the player.
Yoosung is close with Jaehee, and Jaehee watches out for him and nags him to get his life together frequently. Jaehee watches out for Yoosung's health and his gaming addiction. Yoosung brings up at one point that he sometimes sees Jaehee as an older sister looking out for him. In the Christmas special, Yoosung and Jaehee work together for the C&R fundraiser. Jaehee says she is proud of Yoosung for working so hard.
Yoosung is jealous of Jumin's good looks and money and will often tell the player to stay away from him. Other than that, Jumin and Yoosung are good friends, and at some point Jumin hired him as an intern. Jumin also give Yoosung the kitten, as seen in the After Ending, whom he named Lisa.
His mother who took as much care of him as she could and sent him to college. Ever since his mother became sick he promised to visit her more often.
Yoosung is shown to care greatly for her, despite her not being his own dog. Her death is the reason he became a veterinarian.
In his After Ending, she has been adopted by Yoosung. However, in any other route they have no relation.