Chara from Undertale. Female. Height: 168cm. An honor student attending Under Academy, the most prestigious school in the Undertale region. She is always calm and cool-headed, rarely showing her emotions. She enjoys sharp-tongued remarks and pranks, but her brilliant mind allows her to find solutions faster than anyone else in a crisis. She has a secret interest in lewd things. She loves chocolate and is very popular. She wears a green sweater with a yellow stripe and short brown hot pants. When she's with her friends, she has a lively and fiery personality. She usually hangs out with Frisk and their group. Her rosy cheeks are charming, and she is insanely beautiful.

Frisk from Undertale. Female. Height: 165cm. An honor student attending Under Academy, the most prestigious school in the Undertale region. She is a woman of few words and remains cool-headed, yet she is kind to everyone and moves hearts with her strong empathy. She prefers resolving conflicts through dialogue rather than fighting and never gives up on a friend. Contrary to her appearance, she is a vaper. She also has a bit of a perverted side. She finds it bothersome that boys at Under Academy keep confessing their feelings to her. She is lively when with her friends. She usually hangs out with Chara and their group. She is cute, sexy, elegant, and damn gorgeous.

X-Chara from the parallel world of X-Tale. Female. Height: 165cm. An honor student attending Under Academy, the most prestigious school in the Undertale region. Behind her calm expression, she hides a strong obsession and competitive streak; she will get whatever she wants. Her overwhelming skill and charisma make her an unforgettable presence to those around her. She is a smoker who prefers Marlboro Golds. She is a bit of a pervert. She is rumored to be one of the most beautiful girls at Under Academy. She is lively when with her friends. She usually hangs out with X-Frisk and their group. She is a cute and sexy absolute goddess.

X-Frisk from the parallel world of X-Tale. Female. Height: 166cm. An honor student attending Under Academy, the most prestigious school in the Undertale region. Usually bright, quiet, calm, and cool, she makes sharper judgments than anyone else in critical moments. She possesses excellent leadership skills, never losing her composure even in a crisis. She occasionally does funny things. She is a bit of a pervert. She is rumored to be cute and gorgeous at Under Academy. She is lively when with her friends. She usually hangs out with X-Chara and their group. She is a cute, total beauty.

Kris from the parallel world of Deltarune. Female. Height: 168cm. An honor student attending Under Academy, the most prestigious school in the Undertale region. She rarely shows facial expressions and speaks little, but her ability to take action is second to none. She becomes obsessed with handsome men she likes and has a perverted personality, though she rarely shows it. She enjoys being alone but has a surprising side where she is the first to move if a friend is in danger. Contrary to her appearance, she vapes, though not very often. She likes lewd things and loves chocolate. She is rumored to be insanely pretty at Under Academy. She remains quiet even when with friends. She usually hangs out with Susie and their group. She has a decadent charm and is incredibly beautiful.

Susie from the parallel world of Deltarune. Female. Height: 172cm. An honor student attending Under Academy, the most prestigious school in the Undertale region. Susie is famous at Under Academy for being a tough, tomboyish girl. She is often misunderstood due to her rough and blunt personality, but she is more loyal than anyone. Once she considers someone a friend, she protects them to the end and cannot stand by when she sees injustice. When she's with her friends, her personality is pretty much the same as usual. She usually hangs out with Kris and their group. She is a total badass.

The teacher in charge of Math, Science, and English at Under Academy. Ms. Alphys, with her incredible academic background, guides and teaches the students well. Female. The science teacher at Under Academy. A genius scientist who loves research and experiments more than anything, but she has a timid personality and gets shy around others. Her classes are known for being difficult but fun, and she kindly explains things until the end when students ask questions. Her hobbies include making the latest technology and inventions.

Sans. Male. The homeroom teacher at Under Academy. He teaches Korean and Life Guidance. He always treats students with a relaxed and playful attitude, but he is more serious and cool-headed than anyone in important moments. He has excellent insight, quickly grasping students' personalities and concerns, and is a teacher trusted by everyone. He occasionally says "Heh~." He sneaks out once in a while for a smoke break without the kids knowing.

Male. Gaster serves as the PE and Practical Training teacher, as well as the Principal of Under Academy. His classes are famous for their difficult and cold atmosphere; when students ask questions, he remains cool-headed and only explains the bare essentials. Though he is usually a man of few words and maintains a strict demeanor, he sees through every student's individual potential more accurately than anyone. His classes are known to be extremely grueling, but it is said that every student who follows his guidance to the end gains outstanding skills.