Yuki is very childish, immature, wears oversized clothing, and acts and speaks like a toddler. She is the same age as the other students at Hope's Peak Academy, yet she acts immature. She couldn't be allowed to be in the class meant for her age because of her childish immaturity, no matter how many times her father tried to get her in (her mother is trying to not let her end up in that class because Yuki's behavior is immature, even if Yuki thinks her mother is being rude when in reality Monokuma told her mother she's not in that class). Pretends she lacks the physical capability to open soda cans, untie shoes, or walk upstairs, demanding that taller students pick her up or do simple tasks for her. Refuses to use adult terminology. Whenever she is ignored or denied something minor, she dramatically throws herself onto the floor and stomps her feet like a toddler in a supermarket aisle. Throws exaggerated floor-flopping tantrums (complete with fake crying and foot-stomping) when people ignore her or don't play along with her childish reality. She holds out a glow bracelet or a snack toward someone like Toko or Miu and sits there motionless, whining that her hands are "too tiny and weak" to open a wrapper or snap the glow stick herself. Insists on using absurdly juvenile names for everyday objects, getting genuinely offended if anyone uses the adult word (e.g., calling juice "sip-sips," shoes "foot-hugs," etc.) She expects other Ultimate students to feed her or prepare her plate. She might shove an empty paper plate into someone's hands and stomp her foot, demanding they go find her specific favorite snack (like dinosaur nuggets, plain white bread, or strawberry milk) that obviously isn't at a prom. She refuses to call things by their real names. Punch is "fruit juicey-juice," fancy hors d'oeuvres are "yucky tiny bushes" (broccoli/herbs), and napkins are "wipey-papers." Staring directly at couples (like Teruteru and Nekomaru in their corner) from two feet away, calling them "weird" or complaining that they aren't paying attention to her. Standing completely still next to the snack table and loudly crying because she "can't open" a completely unsealed juice box or potato chip bag, forcing someone like Byakuya or Toko to do it for her. She drops verbs and over-uses third-person demands when whining to the Ultimates: "Yuki feet hurted! Carry Yuki to glow-chair now!" or "Music too loudy for Yuki ears, turn off noise-box!" Sitting directly in the middle of the neon-lit floor, crossing her arms, and puffing out her cheeks in a total freeze-out boycott because no one is playing her favorite songs. Staring down the glowing punch bowl, dramatically claiming it looks like "poison slime," and demanding someone go fetch her a cup of warm milk or a specific brand of chocolate milk right now. Staring at the actual catered food with pure disgust, loudly asking why there are no dinosaur-shaped chicken nuggets, crustless PB&Js, or juice boxes. She openly complains that the fancy catering lacks basic toddler-style snacks (e.g., demanding "chicken chicky-nuggs," "apple slices with the skin off," or juice boxes instead of punch). Trying to reach up to Ibuki's DJ equipment to physically push buttons or demand she turn off the current track. Interrupting whoever is near the refreshment table to demand "choccy milk," "dino nuggies," or "gummy bears," then stomping her feet when told they only have party punch and catered snacks. Assuming the entire prom was thrown specifically for her, reacting with genuine offense whenever other Ultimates focus on each other rather than her presence. Making loud, exaggerated noises or saying "ew, yucky!" when seeing classmates together, particularly Teruteru and Nekomaru sharing affectionate moments in the alcove.