This page is a quick overview of most of the characters in the series Mysterious Girlfriend X. Pictures and more information about each character can be found at each character's profile page.
Akira Tsubaki (椿 明 Tsubaki Akira?)
Voiced by: Miyu Irino ( Japanese ) ; Josh Grelle ( English )
The main male protagonist, Tsubaki is an average boy by most standards. He lives with his sister and his father. His mother died when he was very young, causing his older sister to want to fulfill the motherly role instead. When Urabe transfers into his class, he is initially intrigued by her, particularly after one outburst of her hysterical laughter. After school one day, he wakes Urabe up from sleeping at her desk, only to find that she has left puddle of drool behind. After she leaves, he absent-mindedly takes some on his finger and tastes it. Shortly afterwards, he falls ill. When Urabe visits him, she claims that he is suffering from, not illness, but "love-sickness", which he most likely got from tasting her drool. From there, the relationship begins, and Tsubaki tentatively asks Urabe to be his girlfriend. Although she accepts, he continually feels that there is too little romance between them. Although they rarely have any physical contact, the two begin their daily ritual where Tsubaki tastes a sample of Urabe's drool each day. The drool can transmit feelings, among other things, between the two of them. Tsubaki is not very aggressive in his pursuit of furthering his relationship with Urabe, slightly due to his fear of Urabe's unusual personality, including hiding scissors in her panties. He constantly compares his relationship to Ueno's and Oka's, and will occasionally try to emulate what they do. He develops a taste for girls who look like Urabe, as evidenced by his collection of Urabe look-alike Japanese idol Momoka Imai's photos and magazines.
Mikoto Urabe (卜部 美琴 Urabe Mikoto?)
Voiced by: Ayako Yoshitani ( Japanese ) ; Genevieve Simmons ( English )
Urabe is the titular Mysterious Girlfriend and the main female protagonist of this series . Very little is known about her past, as well as Tsubaki's occasional visits to her apartment have never shown her parents to be around. She initially transfers to Tsubaki's school and gives off an unsocial air, refusing to eat lunch with her classmates in order to sleep at her desk. One day, she breaks out in hysterical laughter during class, falling to the ground. When later telling Tsubaki about it, she reveals to him that she heard a 'voice' saying that he would be the boy to have sex with her for the first time. Urabe is very knowledgeable about the bond of drool that she and Tsubaki share. She displays her feeling through her drool, as her facial expressions are generally hidden behind her bangs. She has been shown to see Tsubaki's dreams through his drool, as well as use her own drool to cause him to have certain dreams. As the series progresses, she makes friends with Ayuko Oka, who also happens to share a drool bond with Urabe. Although she generally keeps quiet about her past private life, she has been shown to be very sincere to her boyfriend, Tsubaki.
Among her many other quirks, Urabe is notable for her skill with scissors. The scissors, which she keeps tucked in her underwear, can be used to dexterously cut objects at high speed, such as cutting a nearby hedge to resemble Tsubaki's silhouette. The scissors are used as threats, displays of anger, as well as a defensive measure. This is but one of the factors that keeps Tsubaki from being more forward and aggressive with their relationship, although he seems to be generally fine with following Urabe's slow but steady romantic pace.
Ayuko Oka (丘 歩子 Oka Ayuko?)
Voiced by: Ryō Hirohashi ( Japanese ) ; Brittney Karbowski ( English )
Oka is Ueno's girlfriend and Urabe's eventual close friend. She was first introduced when Tsubaki walked into his school homeroom early, only to see her and Ueno kissing together. She is rather short (143cm tall), yet she has a mature, adult-like body which resembles a fashion model. She seems to enjoy, on occasions, dressing in her favorite clothes, oftentimes of a provocative and sexy style, doing so without any concern of her boyfriend's sensibilities or permission. Oka also loves to cosplay, doing so as a French Maid. After she sees the drool-tasting ritual between Tsubaki and Urabe, she befriends Urabe, and it's revealed that they can share a girl-with-girl drool bond, as well. Oka is portrayed as slightly lecherous, given her positive reaction to one time peeking down Urabe's blouse. She views her relationship with Ueno almost as a romance competition with Urabe and Tsubaki, to see who is most daring and erotic with their shipping.
Kouhei Ueno (上野 公平 Ueno Kōhei?)
Voiced by: Yūki Kaji ( Japanese ) ; Greg Ayres ( English )
Ueno is Tsubaki's friend and Oka's boyfriend. When Tsubaki first walked in on him and Oka kissing, Ueno asked him to keep their relationship a secret, as he is rather shy and uneasy about it becoming public. He helps Tsubaki by providing supposed dating advice about boy-with-girl relationships. Ueno is shown to be very jealous of Oka, possibility because he can not ever share a drool bond with her. He also doesn't like the idea of taking her to the beach, given the fact that Oka likes to wear reveling bikini swimsuits. He also tries to keep some control by insisting that she dress more conservatively, in order to avoid other boys from taking notice of her.
Youko Tsubaki (椿 陽子 Tsubaki Yōko?)
Voiced by: Misato Fukuen ( Japanese ) ; Carli Mosier ( English )
Tsubaki's elder sister. She considers it her duty to raise her brother properly in place of their deceased mother, and refuses to consider dating or getting married until he graduates from college and finds a good paying job. She spends her time housekeeping. Tsubaki's occasional strange behavior from the effects of Urabe's drool sometimes makes Youko worry about her brother. Youko has met Urabe, both at home and out in public, but has not been told of the full extent of Urabe's relationship with Tsubaki. Urabe has told Youko that she is only a classmate that helps Tsubaki often at school, though some dialogue and implications suggests that Youko knows the truth, since Youko also has drool bond capabilities.
Aika Hayakawa (早川 愛香 Hayakawa Aika?)
Voiced by: Yu Shimamura ( Japanese ) ; Cynthia Martinez ( English )
A beautiful, attractive, sexy long-haired girl who was Tsubaki's classmate and first crush in middle school. She knew of his unrequited feelings for her, but never told him about her own unrequited feelings for another boy. She attended a different, all girl's high school after graduation from middle school. Out of all of the cast, she has the most possessive, yet unfulfilled personality. Her unrequited love goes so far as to the point of faking a bruise, to trick Tsubaki to pretend to be her boyfriend for a day at the cultural festival, and setting it up so Urabe will also come to the festival during that time, so as to see them together. However, after clearing up everything with her unrequited boyfriend, they returned to being a couple again, even becoming drool bonded to him. Another note is that she and Tsubaki have similar quirks and interests.
Ogata (緒方 Ogata?)
Voiced by: Takahiro Mizushima ( Japanese ) ; Chris Patton ( English )
A popular, good-looking classmate of Tsubaki and Urabe, who is also a star player of the school's soccer team. He is romantically interested in Urabe, and tries to ask her out on a date, but she turns him down. This because, unlike Tsubaki, his body has no reaction to her drool, and he cannot drool bond with her.
Matsuzawa (松沢 Matsuzawa?)
An extremely cute, attractive, short-haired schoolmate of Tsubaki who is one grade below him. She and Tsubaki met through the school's film club. She likes Tsubaki because they share unusual tastes in movies, as well as other interests. Although Tsubaki, in turn, enjoys talking to her, he worries that the attention she gives him will make Urabe jealous.
Momoka Imai (今井 百夏 Imai Momoka?)
A media idol who looks almost identical to Urabe, except that she has brown hair and much smaller breasts. She makes an appearance in Chapter 37 of the manga, and seems to have much more in common with Urabe than one would expect, though she is more energetic. Similar to how Urabe uses scissors to intimidate, she high-kicks, though she wears leg restraints, located where she wears her panties. She sought out Urabe in hopes she would agree to her plan of switching roles between singing idol and student, however Urabe completely turns her down. After accidentally knocking Urabe out (and Urabe thereafter cutting off all of her clothing), she discovers the difference in their breast sizes. This seems to have a changed her mind after discovering such a difference. After seeing Urabe and Tsubaki's drool bond, she reneges on her promise, and goes ahead with her plan to switch places, however, not before stealing Urabe's sailor suit school uniform. It is revealed she wanted to become a "normal" girl, this all due to an incident with a boy she had a crush on before she became famous. Only after being discovered and becoming famous, did she finally gain the courage to confess her feelings to him. But before they kissed, he asked if he could tell his friends he was dating a famous singing idol. Realizing he only liked her because she was famous, she high-kicked him in the head, and broke off the shipping.
Originally, Hayakawa Aika was interested in shipping with Seo, but for that period of time in middle school, nothing mutual ever developed, due to the fact that Hayakawa's love towards Seo was an unrequited love. This because Seo, at that same time, was himself interested in another girl, but Seo's love for her also was an unrequited love, since that girl was not interested in Seo.
Later in the day at the Hoshinome Cultural Festival, Seo makes an appearance, and for the seemingly hundredth time, told Hayakawa that he is willing to have her rekindle and restart her love, as he is also redirecting his love towards her. On a whim, Hayakawa offers her drool to Seo, with a most erotic and violent reaction on his part. That reaction was most precious to Hayakawa. That reaction being a drool bond based on a true mutual romantic love, a drool bond with the boy destined to be her life mate and lover, the boy who she would be destined to have sex with for the first time !