Note: Naming conventions follow the Western system: family name (last name) after the given name (first name). . In the website of the XRATED video game the original Japanese order (family name before the given name) of romanized names is used .
is the main female character, and is childhood friends with Takaaki. Although in the beginning of the game she is still in junior high school, she joins him in the same high school at the beginning of the new school term. Konomi has a friendly disposition, and is often smiling and happy. She sometimes tries hard at cooking, and enjoys being with Takaaki.
is also childhood friends with both Konomi and Takāki: the two see her as an older sister. She left them when they were both children, having to go to an all-girls boarding school. Her promise to come back to Takāki and Konomi in the final year of high school is what prompted her to leave her boarding school. In the game, she is one year ahead of Takaaki.
She is very confident and comes from a rich family. She is well versed in traditional Japanese arts and traditions, yet still is a modern girl in her own right. In her group consisting of Konomi, Takāki and Yūji, she is the strong and dominant personality and acts as the older-sister figure. She often addresses herself as "Tama-oneechan".
In the game's Tamaki scenario, she is followed by a group of three girls from her boarding school. The three attempt to separate her from Takāki as they are "in love" with her. In the process of evading the girls, she declares Takāki to be her boyfriend and proves it with a kiss: at which point the three girls realise they have failed and return to their school.
is in the same grade as Takaaki and the founder and only member of the "Mystery Club" before she manages to blackmail Takaaki into joining. Despite the name, the "Mystery Club" does not really read mystery novels or engage in real-life detective work, but is more a club for the occult, the supernatural, and unexplained. Most consider Karin an oddball, not only because of her interest in UFOs, but because of little things, such as her love for egg sandwiches and singing an odd nursery rhyme about eggs, as well.
is the older Himeyuri twin. She is one school year younger than the protagonist, and helped develop the next generation maid gynoids for Kurusugawa Electronics. While she's quite bright in the technical aspect, to others, she seems quite naive and almost childish. Despite her childish attitude, Sango appears to be the "older sister" of the pair and often gives advice to her twin sister, Ruri.
Both her and Ruri, speak with an extremely strong Kansai (Osaka) dialect.
is the younger Himeyuri twin. She is one school year younger than the protagonist, and is in the same class as Sango. She is fiercely protective and possessive of her sister, and when Sango finds herself attracted to Takaaki, Ruri becomes jealous and even hostile towards him. She is an excellent cook, as well. Unlike her twin sister, Ruri is not very bright and cannot develop robots.
is in the same grade as the protagonist from a neighbouring class and close friends with Manaka. She is very high-strung and aggressive who rides a bike, and for some reason always collides with Takaaki in many embarrassing situations. This is not helped by the fact that she always holds Takaaki at fault, and her attempts to challenge him to duels always end up worse off than they began. After losing to Takaaki in any way, she often points to him and famously says, "Don't think you've already won this!" She lives in a rich family and is being trained to take over her grandfather's business.
An alien that can communicate with animals. Notable also for other traits, like using matchsticks as currency, writing in Egyptian hieroglyphs, raising her arms and speaking out "Ruu" (Which becomes a trend as a silly way of greeting people), and referring to all humans as "Uu".
is one of the protagonist's classmates and the class representative. She likes to help others out to the point that few realize she is being overburdened by her work. Despite being a good class rep, she has a fairly docile personality otherwise. Manaka assists the library club in marking archived books for barcoding, which causes a few problems since she is not a member. Has a talent for blending tea, which she does as a hobby. She is shy around boys, something Takaaki can empathize with. Despite being busy helping everyone at school, she still makes time to visit her younger sister, Ikuno (who is suffering from the complications of diabetes), who is in the hospital.
is a mysterious girl that Takaaki meets in school at night, and for some reason she isn't usually seen. She carries around a notebook called the "Trash Basket Notebook". In the anime, she is seen in a flashback as a young girl who is crying because she is moving away.
is a new character for the PC version only. She is one school year older than the protagonist and the student council vice-president and later the president. She has a cold demeanor and strict attitude and as a result, her only friend is Marianne. When it is time for Marianne to graduate, Sasara is saddened because her only friend would be leaving her and even tries to convince Marianne not to graduate. Takaaki becomes acquainted with her after he is chosen to be a volunteer to help the student council with an event, but when Sasara becomes president, she appoints him as vice-president.