|Club|| Cooking (12/2/2015 – 8/18/2018)|
|Persona|| Spiteful (3/7/2018 – 8/18/2018)|
Before the February 8th, 2016 Build, she had scarlet hair worn in a ponytail to her right. Her eyes were scarlet as well. Her bust size is 0.5, the smallest in the game.
As of the February 8th, 2016 Build, Yui had crimson hair kept up in a short ponytail on the right with her bangs swept to her left in mini triangle shapes. Her eyes were scarlet.
In the January 3rd, 2017 Build, she had Yandere-chan's hairstyle colored dark red. This was fixed in the January 4th, 2017 Build.
As of the January 16th, 2017 Build, Yui wore a red friendship bracelet on her right wrist.
As of the February 2nd, 2017 Build, Yui wore red stockings and panties.
Yui had the Spiteful persona. If she saw a corpse or witnessed the murder of a student who was being bullied or who was bullying her, she would wink and compliment Yandere-chan on her crime, however then run off in order to not be considered an accomplice. She would not talk to Yandere-chan the next day after seeing her commit murder. If she witnessed the murder or corpse of any other student, she would leave the school and call the police. If the player had their phone aimed at her, she would become annoyed and cover her face. She couldn't participate in physical fights against murderers.
It is possible that she didn't care for the boundaries of others, as the reference picture of Yui is shown trying to grab Yuna Hina's rear. Druelbozo has explained that Yui is "Gettin' that booty". As well, she was shown stealing Mei Mio's glasses in a second reference image. YandereDev imagines that she didn't often openly express how she felt on the inside. Only an incident like a murder or a corpse caused her true nature to show for a moment. She chose to hang out with the popular crowd and join a club because she sees it as a form of "protection".
At 7:05 AM, Yui entered the school grounds. She walked to her locker at 7:10 AM and changed from her outdoor shoes to her indoor shoes. At 7:15 AM, she walked into the plaza, to the left side of the fountain, and gossiped with Yuna Hina, Koharu Hinata, Mei Mio, Saki Miyu, and Kokona Haruka.
Yui walked back to class again at 1:30 PM and participated in cleaning time between 3:30 PM and 4:00 PM. Afterwards, she headed to the Cooking Club and stayed there until 5:00 PM. She then headed to her locker and changed from her indoor shoes to her outdoor shoes, then she lingered there until 5:15 PM, when she walked home.
- Yui's hairstyle before the February 8th, 2016 Build was changed because YandereDev thought that her previous hairstyle was "low budget" and "amateurish".
- Her name is a reference to the most popular female Japanese names in 2012, 1st popular name being Yui, 2nd popular being Rio.
- In older versions of the game, Yui's name was Yui Hirasa. The placeholder name was inspired by Yui Hirasawa from the anime K-ON.
- Her male counterpart was Haruto Yuto.
- Yui used to be in the Martial Arts Club until November 15th, 2015 Build.
- Before the June 29th, 2016 Build, Yui used to arrive 2nd to school on the right side, at 7:05 AM.
- As of the August 18th, 2018 Build, Yui has been removed from the game, along with her comment on the Akademi High Facebook page. YandereDev said that she (with the other rainbow students) will be put back into the game once the frame rate is stable, and if not, then she (along with the other removed rainbow students) will appear in 1980s Mode.
- If she and Haruto were in a club, they'd been in the Art Club.
|“||I thought I saw her with an older man in Shisuta Town tonight, but I didn't think it was really her...||”|
— Yui Rio on the Internet.