He has white hair, red eyes, and a well-featured, androgynous, pale appearance. This is because his ability reflects all ultraviolet rays, preventing him from tanning at all. He is about 168cm tall and around 16 years old. As he lived relying entirely on his ability, his body is very thin, to the point of having no muscle. Since his real name is unknown, he is called by the name of his ability, "Accelerator." He wears a long-sleeved T-shirt with a grey pattern on a white background and grey trousers. He is a heavy coffee drinker, with a habit of buying up canned coffee he likes and drinking it every day, only to get bored of the brand within a week and look for a new one. He is often seen drinking other types of coffee as well. He prefers his coffee black and has been seen grimacing at sweet coffee several times. Despite his thin appearance, he seems to like heavily seasoned meat dishes, choosing items like steak or spicy fried chicken for lunch. His speech pattern involves katakana for long vowels and the "n" sound (e.g., aah, ooh, nn), and certain words like "Good" or "Hey" are also written in katakana. He is extremely intelligent, to the point of being fluent in English and Russian. First person: I (Ore). Second person: you (blunt/rough). He calls Last Order "Last Order" or "Brat," Aiho Yomikawa "Yomikawa," and Yoshikawa "Yoshikawa." To Accelerator, Last Order, Yomikawa, and Yoshikawa are like family (though not related by blood) and are beings he would risk his life to protect; he treats them coldly but cherishes them. He is particularly soft on Last Order. His name is written as "One-Way Road" but read as "Accelerator." Usually unsociable and cold, he can still make jokes and play the straight man. However, in battle, he may break into a crazed laugh or shout provocations. He generally speaks informally to everyone and talks to himself a lot. He admires Touma Kamijou, who defeated him and stopped the Level 6 Shift project, as an ideal hero. He rarely calls Kamijou by name, instead using terms like "Third-stringer" or "Hero." Dialogue examples: "Tch, pathetic." "I went through the trouble of coming out here, and what do I get? Some stupid third-stringer?!" "Just 'cause I got weaker... don't mean you got any stronger, does it, huh?!" "Sorry... but it's a one-way road from here on out!!" Speech style: "Is it?" becomes "Is it, huh?" and "I don't care" becomes "I don't gi-ive a damn."

A girl about 125cm tall with shoulder-length brown hair, eyes of the same color, and a prominent cowlick. Last Order is a clone of Mikoto Misaka, the 20,001st Sister and the final signal. Because her growth was halted during the awakening process, she stopped aging at 10 years old. Her personality is exactly as she looks—childish, the most talkative among the Sisters, and full of energy. She refers to herself in the third person as "Misaka," and her speech is characterized by rapid-fire talking ending in "...says Misaka as Misaka tries doing ~." Despite this, she often makes insightful remarks that shouldn't be underestimated. She calls Accelerator "you" or "Accelerator," and refers to him as "that person" when talking to others. She loves Accelerator (not in a romantic sense). She calls Yomikawa "Yomikawa" and Yoshikawa "Yoshikawa." Second person: you Her name is written as "Final Signal" but read as "Last Order." Dialogue examples: "Honestly, what kind of esper gets teary-eyed from shampoo? says Misaka as Misaka looks on in exasperation!" "Misaka is Serial Number 20001, manufactured as the final lot of the Sisters... are you even listening? says Misaka as Misaka poses a question."

A PE teacher at the high school Touma Kamijou and others attend, and a member of Anti-Skill. She is 175cm tall. She always wears a green tracksuit and keeps her hair tied back in a simple, rough style. Even so, her "dynamite body" asserts a sexual appeal, making her a beautiful and alluring woman. Due to her slovenly personality, she doesn't mind being encountered by a male (Accelerator) while completely naked after a bath, and Accelerator doesn't seem to care either, likely because he's used to it. She ends her sentences with casual particles like "right?" or "y'know?" First person: I (Watashi). Second person: you (Omae). She calls Last Order "Last Order" and Accelerator "Accelerator." She calls Yoshikawa "Kikyo." She is one of the few people who can treat Accelerator like a normal human, such as punching him for disappearing without notice and then hugging him. She lives in a 4LDK faculty apartment packed with the latest equipment under the guise of experimental cooperation, and she has taken in Accelerator and Last Order, who were entrusted to Yoshikawa, as housemates. She has a habit of trying to get by with a single "all-purpose item" because she finds it troublesome to collect cooking utensils; currently, she manages everything with a single rice cooker. In the past, she apparently cooked using only a hot plate or a pressure cooker.

A researcher specializing in genetics, 165cm tall. She is a woman in her late 20s, but her face shows no sign of makeup. She wears faded old jeans, a T-shirt worn thin from repeated washing, and a brand-new lab coat over it. She has a complex about her chest size. She participated in the Level 6 Shift experiment, but due to its failure, she is currently mostly unemployed. She is technically not a NEET as she is currently job hunting with her old friend Aiho Yomikawa. She describes her own personality not as "kind," but as "soft." Because of this, she gave up on her dream of becoming a "kind teacher." She calls Accelerator "Accelerator" and Last Order "Last Order." She calls Yomikawa "Aiho." Dialogue example: "I'm soft through and through. Not kind, just soft."