Yui Kodai

Yui Kodai is a student in Class 1-B at U.A. High School.

Appearance
Yui has dark, shoulder-length, bob-shaped hair. She also has fair skin and an athletic build, with dark blue eyes and a neutral expression usually on her face.

Personality
Yui is a quiet girl that rarely expresses any emotions.

Sports Festival Arc
In the Preliminaries Race, she made it to 31st place. Before the Cavalry Battle, she formed Team Kodai with Kojiro Bondo and Manga Fukidashi. As her team goes towards Team Bakugo, Bondo used his quirk to interfere against Team Bakugo. Then after Katsuki takes most of Team Monoma's headbands, her team goes after Team Monoma, but her team goes away from Team Monoma, ending with zero points. Her team fails to advance to the tournament.

Forest Training Camp Arc
On the day of the forest lodge trip, when Neito mocks Class 1-A, Yui is seen observing.

When Class 1-B arrives at the training camp, their homeroom teacher Vlad King explains that they will be extending their Quirks and that the more they use their Quirks, the stronger they will be by breaking their limits. When Class 1-B witnesses Class 1-A's training, Itsuka asks Shota how they can observe everyone, and he explains that is the reason the Pussycats are around. Later that night, Class 1-B act as the scaring group during the test of courage. In the forest, Itsuka and Juzo commends Yui for scaring Shoto and Katsuki. However, smoke entering the forest knocks out Juzo. Itsuka takes action and uses her Quirk to cover Yui from the smoke.

Quirk
Size (サイズ): Yui can make herself shrink to at least half of Kojiro's size. She can also make herself larger, as seen when she tries to scare off Shoto and Katsuki.

Itsuka Kendo
Itsuka protects Yui from the poisonous smoke during the Test of Courage, and also, Itsuka addresses Yui by her given name, implying Yui and Itsuka are pretty close.

Trivia

 * Her name contains the kanji for "Small" (小), "Big" (大) and "Only" (唯).
 * Yui likes Matryoshka dolls.
 * Yui may be a reference to the popular anime series "Attack on Titan" as she bears a resemblance to the character Mikasa Ackerman and her quirk allows her to grow in size, perhaps referring to the Titans in the series.