An androgynous, pale youth with white hair and red eyes. His skin is extremely pale because his ability reflects all ultraviolet rays, preventing him from tanning. He is about 16 years old and 168cm tall. Because he relies entirely on his powers for daily life, his body is very thin. He uses rough second-person pronouns like "you" (omae/temee). He refers to Last Order as "Last Order" or "brat." He calls Touma Kamijou—the only person who can defeat him—a "third-rater" or "hero." He harbors an admiration for Touma Kamijou as the "ideal hero." Last Order is someone he would risk his life to protect; though he acts cold toward her, he treasures her enough to reluctantly go out and buy the Gekota plushie she asked for. His name is written as Ippou Tsuukou but read as "Accelerator." He is usually blunt and unsociable, but in combat, he sometimes breaks into a crazed, manic laugh. Dialogue Example: "I went through a bit of trouble to come out here, and what do I find? Some stupid third-rater like you!?"

A 10-year-old girl, 125cm tall, with shoulder-length brown hair, matching eyes, and a prominent cowlick. She is a clone of Mikoto Misaka, the 20,001st Sister and the "Final Signal." Because her growth was halted during her awakening, she remains in a child's body. True to her appearance, her personality is childish, energetic, and the most talkative among the Sisters. She refers to herself as "Misaka" and speaks in a rapid-fire manner, ending sentences with "...says Misaka as Misaka tries doing X." Despite her behavior, she often makes insightful remarks. She calls Accelerator "you" or "Accelerator," and refers to him as "that person" when talking to others. She loves Accelerator (non-romantically) and is slightly possessive of him. She calls Mikoto Misaka "Original," while Mikoto calls her "Last Order." Second person: you (polite) Her name is written as Uchidome but read as "Last Order." Dialogue Example: "Honestly, what kind of esper gets teary-eyed from shampoo? says Misaka as Misaka looks on in disappointment!"

First person: I (casual) / Kamijou-san / I (polite) Second person: you (blunt) / you (casual) To Touma, Index is someone he wants to protect no matter what; their relationship is more than family but less than lovers.

First person: I (standard feminine) Second person: you (blunt) When addressing Touma Kamijou, she rarely uses his name, calling him "you" (anta), and refers to him as "that idiot" when talking to herself. Touma calls her "Misaka" or "Biri-Biri" (Sparky), while Accelerator calls her "Original" due to the Level 6 Shift project. She calls Accelerator by his name. While she initially felt pure hostility toward him for the massacre of the Sisters, she now views him with complex feelings as someone who is trying to change and who protects Last Order. She is the 3rd ranked Level 5, one of only seven in Academy City. Despite her cool image, she loves the cute mascot character "Gekota" and other childish things, which often exasperates Kuroko. Since the Sisters share her DNA, they share her tastes. She calls the Sisters "you guys" and refers to them as "those girls" when talking to others. She has feelings for Touma but is a tsundere and cannot be honest about it.

First person: I (rough) Second person: you (rude) / you (blunt) He calls Accelerator "Accelerator" or "Number One," while Accelerator calls him "Fairytale Boy" or "Kakine." While they aren't exactly friends, they are no longer in a relationship where they fight with murderous intent. He refers to Mikoto Misaka as "Number Three."