Hitoshi KobeA socially awkward high-school student with a talent for creating A.I. programs.
- The Chew Toy: As typical of Akamatsu's male leads, he takes a lot of punishment.
- Covert Pervert: He's noticeably less inhibited than Keitaro and Negi.
- Expy: Of Kei'ichi from Ah! My Goddess.
- Groin Attack: The best example is in Chapter 35, which revolves around this trope. In frustration over Hitoshi's constant perviness, Toni and 30 challenge him to go an entire day without getting aroused. They do this by placing him in a high tech chastity belt that has a little priest with a paddle over the crotch; if it detects a 'stirring in the loins' so to speak, poor Hitoshi gets whacked, and on the last activation the belt will detonate. Toni sets it to 30 activations, claiming that nobody's that much of a sex fiend, but Hitoshi proves her wrong in the most painful way; getting whacked 14 times in just the morning. Eventually, he makes it through the day with one activation left... until Toni challenges him to find the key to the belt hidden somewhere on 30's body. Predictably, his groin then goes nuclear.
- Raging Stiffie: Hitoshi is the human 'bar' in a beach limbo contest with 30 and the others. When her turn comes round, he's set so low that she's grinding against him - then her boobs get in the way. He lifts up to let her pass, but not before his resultant tentpole nearly wangs (sorry) her in the face. Cue Naru Punch.
Number 30 (Saati Namba)An A.I. program that materialised during an electrical storm.
- Author Appeal: Akamatsu has stated that 30 has such prominent eyebrows because he finds them attractive.
- Characterization Marches On: Starts out as an Innocent Fanservice Girl that lives for Hitoshi. Over time she becomes less of a pushover and regularly chastises Hitoshi for his perverted antics.
- Expy: Of Belldandy from Ah! My Goddess. She's also an unintentional expy of Lisa from Weird Science.
- First Girl Wins: Subverted. While 30 is introduced as Hitoshi's first love interest, she's actually second to 20.
- I Want My Beloved to Be Happy: When it seems like Cyndia might take Hitoshi, 30 willingly steps aside.
- Lethal Chef: Early in 30's cooking lessons, her sole experience with food is looking at pictures of the finished product, not realizing that the dishes must be made of edible ingredients. She cooks using things like watercolor paints and dish detergent.
- Magical Girlfriend: Of the Magitek variety.
- Naked on Arrival: Due to Hitoshi not programming any clothes for her, she first materialises completely nude.
- Nice Girl: The kindest character in the whole series.
- One-Note Cook: Once 30 learns how to cook, she can only make curry, no matter how hard she tries to not make curry.
Number 20 (Toeni Namba)The first fully-functioning A.I. program that Hitoshi created.
- '90s Hair: Towards the end of the series, she cuts her hair to mid-length.
- Characterization Marches On: Starts out as emotionally abusive towards Hitoshi, but develops into a Jerk with a Heart of Gold after hanging out with 30 and 40.
- Cool Big Sis: To 30 and 40.
- Expy: Of Urd from Ah! My Goddess.
- Foil: To 30. While 30 is kind and helpful, 20 is manipulative and insensitive.
- Lovable Alpha Bitch: Gradually evolves into this.
- Shameless Fanservice Girl: Dresses provocatively and flirts a lot.
- The Tease: When she first materialised, 20 tried seducing Hitoshi but was repeatedly thwarted by 30.
Number 40 (Forty Namba)An A.I. program that can alternate their gender and personality.
- Expy: Of Skuld from Ah! My Goddess. 40-kun's appearance and personality are similar to Negi Springfield's.
- Foil: The 40-chan and 40-kun have opposite personalities. The male is well-mannered, while the female is hyperactive.
- Gender Bender: Before 40 was ready, 30 and 20 argued about the gender and personality and pressed too many buttons at once. The end result is an A.I. that has two modes: a male personality and a female personality within a female body - when Forty-kun says "girl", he becomes Forty-chan, when Forty-chan says "boy", she becomes Forty-kun.
- Hot for Teacher: 40-kun develops a crush on his homeroom teacher, only to find out she's engaged and has to resign upon getting married.
Kimika AsoA classmate of Hitoshi.
- Alpha Bitch: She's nasty and conceited towards just about everyone.
- Chuck Cunningham Syndrome: Kimika was the antagonist of volume 1 and two chapters of volume 2 and after that she is never seen again.
- For the Evulz: Pretty much why Kimika Aso antagonizes Hitoshi and later Saati.
- Only Six Faces: Invoked. 20's face was modeled on Kimika's.
NittaA math teacher.
Takako MiyaharaA student who works on the school paper.
Misako Takemoto40's homeroom teacher.
Yuko WatanabeA student librarian.
Kikuko KobeHitoshi's cousin.
Number 29An earlier version of 30.
Yayoi KobeHitoshi's younger sister.
- A-Cup Angst: She's initially very self-conscious about her undeveloped assets, but overcomes her shyness when she realises people like her for her personality.
- Author Appeal: Just like 30, her thick eyebrows were a conscious choice by Ken Akamatsu.
- Big Brother Attraction: Implied with Hitoshi, but never fully addressed.
Ma-kunAn A.I. program that Yayoi created.
Love Rivals & Antagonists
Billy-GA computer hacker.
- Back for the Finale: Billy-G was the main antagonist during the first part of the series, but disappeared after creating a back-up copy of 30 in chapter 20. He finally comes back in the last chapter (55), where he uses the back-up to save the real 30 from deletion, unbeknownst to everyone.
- Evil Counterpart: For Hitoshi. He's possibly more computer-savvy than Hitoshi, but is not above copying Saati's programming.
- No Celebrities Were Harmed: His name is an obvious nod to Bill Gates.
Cynthia McDougalAn American teen idol.
- Ms. Fanservice: She gets a lot of male attention, with her debut chapter focusing on an impending wardrobe malfunction.
- Phenotype Stereotype: Is half-Japanese, but has green eyes.
- The Rival: She gives 30 the most competition for Hitoshi's affections.
Number 0 (Spider-Zero)An A.I. program that was infected by a computer virus.
- Animal Motifs: Spiders.
- Bishounen: His template resembles a pretty teenage boy. His good looks become more sinister the more his programming is corrupted.
- Expy: Fate Averruncus from Mahou Sensei Negima! resembles Zero in looks and personality.
- Glowing Eyes of Doom: Part of his One-Winged Angel form.
- I Have You Now, My Pretty: Upon being corrupted, he takes an interest in 30. Subverted in that his obession isn't sexual, he just wants to consume her data.
- One-Winged Angel: At full power, he grows 4 extra arms and a pair of wings.
- White Hair, Black Heart: Has silver hair and is the cruelest character in the series.