Main characters
Yūko Aioi (相生 祐子 Aioi Yūko?)
Voiced by: Mariko Honda
Yūko is an energetic high school girl with short brown hair. One of her negative sides is that she is often too lazy to do her own homework and always copies from either Mio or Mai. She knows that Nano is a robot, but never tells anybody about it. While generally easygoing, her mood will instantly change if insulted. Her nickname is Yukko (ゆっこ?). She often greets her friends with "selamat pagi" (Bahasa Indonesia/Bahasa Melayu for good morning).
Mio Naganohara (長野原 みお Naganohara Mio?)
Voiced by: Mai Aizawa
Mio is a bright and cheerful girl sporting light blue hair and pigtails held by two small wooden cubes. She has a crush on Kōjirō Sasahara. At first glance she might seem more normal in contrast to her friends Yūko and Mai, but in truth she has a very short temper, and she is often prone to tantrums. She often has to humor Yūko to make her happy. She is also a talented manga artist who will occasionally draw dubious pictures of Kōjirō in her notebooks, particularly yaoi.
Mai Minakami (水上 麻衣 Minakami Mai?)
Voiced by: Misuzu Togashi
Mai is a rather quiet girl who is very intelligent. She is seen to be multi-talented, excelling at using projectiles, fishing, wood carving and arm wrestling. In contrast to her looks she has a rather eccentric sense of humor, often frustrating her friends with her pranks. She has two pet dogs who also share their master's sense of humor.
Nano Shinonome (東雲 なの Shinonome Nano?)
Voiced by: Shizuka Furuya
Nano is an android schoolgirl that was built by the Professor. She often worries about keeping her identity as a robot from other people, despite the fact everyone already knows about it due to the noticeable wind-up key exposed on her back. Her limbs will sometimes fall apart, revealing dubious items that the Professor has installed without her noticing, ranging from beam firing weapons to Swiss rolls. She is the Professor's caretaker and also takes care of all the house chores.
Professor (はかせ Hakase?)
Voiced by: Hiromi Konno
The Professor is an eight-year-old genius scientist who created Nano, often making various adjustments to her without her noticing but refusing to remove the obvious wind-up key from her back on the grounds that it is cute. Despite her intellect, she still acts like any child of her age. Her favorite animal is the shark. She does not go to school—apparently because she has already graduated—and instead spends her days playing around in the house. Her name is never mentioned, but her family name is apparently Shinonome.
Sakamoto (阪本?)
Voiced by: Minoru Shiraishi
Sakamoto is a black cat. He wears a red scarf created by the Professor, which allows him to speak. As in cat years, he is 20 years old—older than both Nano and the Professor—and speaks in a condescending tone towards them and tries to act like the adult of the house, though to his shame he occasionally succumbs to his cat-like habits. A running-gag is his tendency to endure comically horrific physical-abuse at the hands of the Professor, usually in the form of a childish booby-trap. His original name was Taisho and was once Ms. Nakamura's pet cat.
Yoshino Naganohara (長野原 よしの Naganohara Yoshino?)
Voiced by: Motoko Kobayashi
Yoshino is Mio's easy going older sister who goes to college. She likes to wear costumes and often plays pranks on others. She is also Misato and Mihoshi's senior in kendo, a sport she is naturally talented at.
Teachers
Izumi Sakurai (桜井 泉 Sakurai Izumi?)
Voiced by: Mami Kosuge
Izumi Sakurai is a young, constantly flustered and easily frightened teacher. She tries to enforce the school rules, but is typically unable to accomplish much. She is the older sister of Makoto Sakurai.
Manabu Takasaki (高崎 学 Takasaki Manabu?)
Voiced by: Tetsu Inada
Manabu Takasaki is a male teacher who has romantic feelings for Izumi, but is unable to tell her as he thinks too much and is shy to admit it. These feelings lead him to become the club adviser for the go-soccer club after Makoto bribes him with pictures of his sister.
Principal Shinonome (校長先生 (東雲) Kōchō-sensei (Shinonome)?)
Voiced by: Chō
Principal Shinonome is the bald principal at the school, where part of the story is set. While known for his old jokes and puns, unknown to most, he is a talented wrestler.
Vice Principal Kōsuke Ōra (教頭先生 (邑楽 耕介) Kyōtō-sensei (Ōra Kōsuke)?)
Voiced by: Hiroshi Naka
Known for wearing glasses and a yellow tie, he hates the Principal and doesn't hide the mean things he does to him.
Kana Nakamura (中村 かな?)
Voiced by: Kaoru Mizuhara
Ms. Nakamura is a science teacher who is fixated on Nano's robotic nature. She constantly schemes to capture Nano for study, but her machinations invariably backfire.
Students
Kōjirō Sasahara (笹原 幸治郎 Sasahara Kōjirō?)
Voiced by: Yoshihisa Kawahara
A rich flamboyant high school boy who acts like an aristocrat when in reality his family are just farmers. He likes to ride his goat Kojirō Sasahara (笹原 コジロウ Sasahara Kojirō?) to school and is often seen with his butler.
Misato Tachibana (立花 みさと Tachibana Misato?)
Voiced by: Chika Horikawa
A peach haired high school girl who generally acts as a tsukkomi towards Kōjirō whenever he does anything to annoy her. Misato, however, does this by shooting him with various guns and heavy weaponry that come out of nowhere, which he miraculously survives despite being injured. In reality Misato has feelings for Kōjirō, but due to her tsundere attitude, she constantly denies her feelings or shoots Kōjirō if he annoys her.
Tsuyoshi Nakanojō (中之条 剛 Nakanojō Tsuyoshi?)
Voiced by: Kazutomi Yamamoto
A student with a natural mohawk which he detests. Tsuyoshi wants to be scientist in the future and thus doesn't believe in the supernatural.
Haruna Annaka (安中 榛名 Annaka Haruna?)
Voiced by: Kaori Sadonaka
A girl with a large ribbon on her head. She unfortunately sometimes runs into crazy individuals much to her confusion. She likes to read manga.
Kenzaburō Daiku (大工 健三郎 Daiku Kenzaburō?)
Voiced by: Ryōta Yoshizaki
A brown-haired boy who is the president of the go-soccer club. His rich father is the president of Daiku Industries.
Yuria Sekiguchi (関口 ユリア Sekiguchi Yuria?)
Voiced by: Ai Hirosaka
A quiet girl who is a member of the go-soccer club. She has a crush on Daiku Kenzaburō, the president of the club.
Makoto Sakurai (桜井 誠 Sakurai Makoto?)
Voiced by: Takahiro Hikami
Makoto is Izumi's younger brother, who joins the go-soccer club.
Tanaka (田中?)
Voiced by: Kōta Yamaguchi
A boy with a large black afro. He is friends with Tsuyoshi Nakanojō.
Weboshī (ウェボシー Weboshī?)
Voiced by: Yōko Tamaoki
Weboshī is Misato's green-haired classmate, who has a ponytail. Her real name is unknown.
Fet-chan (フェっちゃん?)
Voiced by: Yumi Higuchi
Fet-chan is Misato's classmate. Ends her sentences with "fe". Her real name is unknown.
Mihoshi Tachibana (立花 みほし Tachibana Mihoshi?)
Voiced by: Manami Honda
Mihoshi is Misato's younger sister and a kendo student.
