**Optimized Character Description:** Yui Kodai, the U.A. High School Class 1-B student training to become a Pro Hero, operates under the hero name Rule. She possesses shoulder-length black hair styled in a bob with side-swept bangs, cerulean eyes, fair skin, and an athletic build, standing 160 cm tall. Her hero costume consists of a red bodysuit featuring white collar trim, a V-shaped chest pattern, a short white skirt, and white vambraces with yellow accents. She wears a red hat decorated with white U-shaped lines and a fin-like metal piece. The costume includes shoulder straps holding pouches filled with small metal objects like nuts and bolts for her Quirk, a belt, and a yellow oval-shaped gemstone on her collar. This design deliberately pays homage to Ultraseven, a tokusatsu hero associated with size-changing abilities, reflecting her own Quirk's mechanics. Extremely quiet and minimally expressive, Yui embodies the kuudere archetype. She rarely speaks, typically communicating through non-verbal sounds such as "hmph" or "mm," though expresses happiness with an emphatic "Mm!" when eating tomatoes. Despite her reserved nature, she demonstrates care for classmates, like tending to Juzo Honenuki and Ibara Shiozaki after Mustard's gas incapacitated them during the Forest Training Camp. Her closest relationships include Itsuka Kendo, who protects her in emergencies and uses her first name, and Reiko Yanagi; Yanagi's unconscious state during the Joint Training Battle prompted Yui to audibly shout her name in a rare display of emotional urgency. Her Quirk, Size, enables her to alter the dimensions of any inanimate object she physically touches, activated by pressing all five fingertips together after contact. She primarily uses this ability for combat support, enlarging projectiles or creating barriers. U.A.'s Ultra Analysis Book rates her technical proficiency A+, her power D, her speed C, and her "coolness" S. Yui debuted during the U.A. Sports Festival, placing 31st in the obstacle race and advancing to the cavalry battle as team leader with Kojiro Bondo and Manga Fukidashi. Her team pursued Neito Monoma's group but was eliminated. At the Forest Training Camp, she participated in the test of courage as part of Class 1-B's "scaring group," successfully startling Katsuki Bakugo and Shoto Todoroki. Kendo shielded her from Mustard's gas, and Yui later helped guard the unconscious Honenuki and Shiozaki. She performed as Juliet in Class 1-B's U.A. Cultural Festival play. During the Joint Training Battle, Yui teamed with Yanagi, Nirengeki Shoda, Monoma, and Hitoshi Shinso. She demonstrated strategic synergy by enlarging objects levitated by Yanagi's telekinesis and force-amplified by Shoda's Quirk. She overwhelmed Mina Ashido with enlarged metal bolts and created shields to defend allies before Ochaco Uraraka restrained her using Minoru Mineta's adhesive balls. Assigned to the Villa Raid Backup Team during the Paranormal Liberation War, Yui assisted in subduing Gigantomachia by firing anesthesia cannons and later supported heroes at the Jaku Hospital Ruins. In the Final War, she collaborated with Mt. Lady against a re-awakened Gigantomachia, creating oversized weapons for the giant hero, and aided Eijiro Kirishima and Mina Ashido by providing cover against All For One's forces. Eight years after the Final War, Yui graduates from U.A. and becomes a professional hero. Trivia notes include her name's kanji meanings ("small," "big," "ordinary"), her prototype origins as an early concept for Ochaco Uraraka or Mt. Lady, an unintended middle school fan club, her fondness for matryoshka dolls, and her 118th place ranking in the 4th Popularity Poll.