Yuyu is introduced rather late in season 4 of the anime to help out Nejire with preparations for the beauty pageant that happens every year during the school festival. Multiple times, Yuyu explains to their fellow peers that Nejire is more of the “cute type” rather than the “sexy type”.
Later on, Nejire calmly approaches a blushing Yuyu and introduces her to Midoriya and Mirio, explaining that she originally did the beauty pageant her first year because Yuyu suggested it, but ended up finding it really fun, and continued to participate in them. She adds that since it's now her last year at U.A and her last chance, she really wants to win especially, since she's kept losing to the same girl, Bibimi Kenranzaki.
As the day of the Festival approaches, Yuyu is seen helping Nejire as much as possible to prepare for the parade. Some time later, Yuyu was also present holding Nejire's dress when she hears Monoma telling Itsuka that there is no doubt that she will win. It’s finally time for Nejire to perform, Yuyu can be seen in the audience rooting for her with an intense look on her face, determined for her to win. She explains to the audience why Nejire lost the year before. As Nejire performs using her quirk, Yuyu is in awe, just like the rest of the audience. At the end, Nejire is declared the winner and Yuyu cries with joy at her victory while blushing.
In the volume 4 of the School Briefs, right before the Beauty Pageant, Kendou and Nejire are seen talking together before the Pageant, until Kenranzaki appears right before them and tells Nejire that she wishes that "may the best woman win", which Nejire agrees saying that she was the best and wouldn't lost against her. Kenranzaki then complains about Nejire's dress, saying that she had to change. When she asks why, Kenranzaki apologies, saying that she mistook "that plain old thing for Hado's everyday garb". Nejire seems a little affected by her words, saying that that was mean and the dress was cute. A moment later, when Kendou was going to stop both girls, Yuyu appears to defend Nejire by saying; "Scuse me, Kenranzaki, but could I ask you to back off of Nejire?", which surprises Nejire, Kendou and Kenranzaki because Yuyu appeared from nowhere like a "loyal hunting dog ready to defend its master".
Kenranzaki says that Yuyu didn't had to get really bent out of shape, which left Yuyu with loss of words standing just beside Nejire. After everything calmed down, Yuyu had found a giant nail in Nejire's shoes which made Yuyu get mad, blaming Kenranzaki because she thought that the nail was hers. Nejire stops her by saying that she needed to cut that off, because there was no proof, but Yuyu keep insisting about that Kenranzaki did that to winning again, but Nejire told her again to cut it out. Kenranzaki then offers Nejire to find out the culprit, which she accepts and Yuyu complains about. Nejire says that the more people looking, the better the odds of finding them.
After agreeing to the research, Nejire glances back to Yuyu who was running few paces behind, because she was ready to protest when Nejire volunteered to help but then remained on silent. Kendou interpreted that both girls were fighting, and when Nejire and the other girls were searching for Hatsume's lost gadget, Kendou offered to talk with Yuyu. Yuyu says that she was the one who suggested Nejire for being in the pageant originally, and that she was a total cutie to her. Then she says that she was sure that Nejire would bring home the crown, but Kenranzaki had won the pageant for 2 years in a row, and that if the judges don't see how cute Nejire is, their eyes must be malfunctioning, because nobody in the galaxy can hold a candle to Nejire.
Kendou then thinks: "It's like she's bragging about her amazing sweetheart?" and that thought made warm her heart, but then Yuyu says that she was hurting Nejire for nothing, as for a pageant or not, Nejire was still cute. She says that Nejire wanted to compete and win and Yuyu wanted that so badly for her, that she would do just about anything, but she gets so worked up that it makes Nejire worried about her. This makes Yuyu blame herself, saying that she was the worst. She adds that as they got closer and closer to the big day, she had felt her fuse getting shorter and shorter, making her not even herself. Suddenly, Nejire appears and calls for Yuyu, which surprises both Kendou and Yuyu. Nejire goes to say something to her, but then is interrupted by Tamaki, who had found the culprit.
After catching the culprit, the situation calms down, but Nejire complains about Kenranzaki saying she has no eye for beauty. Yuyu then intervenes saying that Nejire was more a minimalist and cutesy than gaudy, while she was holding back. Nejire walks over Yuyu, smiling and saying that Yuyu was Yuyu, which confuses her. Nejire explains that she saw that she was being not herself and even if she's not acting like herself that it was still a part of Yuyu. No matter what, that is the whole package, and that package was her good friend. Yuyu asks what if she hated some parts of herself, and Nejire says that if that happens, then she just needed to rev herself up. Nejire then says that she would go on win, because that would make Yuyu happy. Yuyu teasingly says that Nejire was a sore loser and Nejire says that she will rev herself up to win the Beauty Pageant.
The Ultra Analysis data book, it is said that Yuyu is Nejire's closest friend and it is revealed that she is also his classmate. In Yuyu's section of the book it is revealed that she thinks Nejire is the cutest person in the galaxy and has helped her in the Cultural Festival Beauty Pageant since her first year. For Nejire's latest beauty pageant, Yuyu guided her to victory by helping her prepare everything from her outfits to the content of her performance.
Relative to most pairings in the show, NejiYuyu is considered a rare pair, mostly due to the lack of screentime for Yuyu. However, the couple has had a good reception despite Nejire's short time with Yuyu on screen due to the additional data they revealed in the fourth Light Novel⁚ One of the reasons why Nejire wants to win the beauty contest is because of Yuyu, while Yuyu wants Nejire to fulfill his wish to defeat Kenranzaki and that the rest of the people see his beauty, besides both girls refer to each other by their first name rather than their last name, indicating that they are close.
Some fans like to theorize that the two girls can be lesbians at some point due to different factors that they find about both. On Yuyu's side her profile reveals that she likes cute things and considering that she constantly refers to Nejire as the most beautiful thing in the galaxy, it may mean that Nejire may be Yuyu's favorite person and in the novel he uses words similar to confessions of love to refer to her, even indicated out by kendo at some point. As for Nejire, shippers like to interpret her love of lilies (yuri on Japanese) as a intentional subtext from the author, or refer to her as seemingly being closer to Yuyu than any of the male characters.
- NejiYuyu is the second most famous femslash ship in the franchise after MomoJiro. When the latter lost some popularity, it also influenced the interest in NejiYuyu, not least due to the fact that is idea is also based on tomboy with a potential crush on her very feminine best friend.