|Club|| Cooking (12/2/2015 – 8/18/2018)|
|Persona|| Teacher's Pet (9/1/2017 – 8/18/2018)|
Before the February 8th, 2016 Build, Mei had blue colored hair worn in tritails, one on each side of her head and one in the back. She also had bangs in the same style as the default Ayano. Her eyes were cobalt blue as well.
Before the May 2nd, 2016 Build, she had cobalt blue hair pulled back into a ponytail with strands of hair that hang to the right, some hair around her neck that reaches her shoulders, and bangs that curl inwards to her cheeks and dark blue eyes. Her bust size is 1.4. She wears blue framed reading glasses.
Before the December 18th, 2017 Build, Mei had blue hair tied in a small bun. Her bangs were longer on her right side, and she had an ahoge on the top of her head. She had a bang going down the middle of her face and another smaller one to the right of the larger bang.
As of the January 16th, 2017 Build, Mei wore a blue friendship bracelet on her right wrist.
As of the February 2nd, 2017 Build, Mei wore blue stockings and panties.
As of the December 18th, 2017 Build, Mei had blue hair tied back into tritails on the back of her head. Her bangs were parted to the right, with a blue hair clip partially holding them back.
As of the January 13th, 2018 Build, Mei's bun was restored, because fans hated the tritails hairstyle she had in the previous build that updated her hairstyle.
Mei had the Teacher's Pet persona. She would give Ayano a suspicious look if she aimed her phone at her. If she saw a corpse or witnessed a murder, she would report to her teacher, unless another Teacher's Pet already had. She couldn't participate in physical fights against murderers.
In her reference photo, she was shown to be studious, as she was seen studying at a desk.
At 7:05 AM, Mei 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 Yui Rio, Yuna Hina, Koharu Hinata, Saki Miyu, and Kokona Haruka.
Mei walked back to class again at 1:30 PM and participates in cleaning time between 3:30 PM and 4:00 PM. Afterward, 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.
- Her name is a reference to the most popular female Japanese names in 2012, the 7th most popular being Mei, the 8th most popular being Mio.
- Name 芽生 Mei means ”Living Bud” (芽 "Me" means ”Bud”, and 生 "I" means ”Living”). Surname 美緒 Mio means ”Beautiful Cord” (美 Mi means ”Beautiful”, and 緒 O means ”Cord”).
- In older versions of the game, Mei's name was Tsumu Kotobu. The placeholder name was inspired by Tsumugi Kotubuki from K-ON.
- Her male counterpart was Ryusei Koki.
- The player can wear Mei's original hair by pressing H. It is the 5th hairstyle. Mei's second hairstyle is the 31st hairstyle available.
- Before the June 29th, 2016 Build, Mei used to arrive on school grounds 5th in line on the left side, at 7:05 AM.
- As of the August 18th, 2018 Build, Mei has been removed from the game. 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. She can now be seen on the street.
- Mei's February 8th, 2016 hair is a reference to Eli Ayase from Love Live! The hair was changed because it was a recolor of a previously existing hairstyle.
- Originally Mei wasn't wearing her glasses because Yui Rio stole them; as of the September 1st, 2017 Build, she now wears them.
- Her hairstyle has been reverted back to her bun as of the January 13th, 2018 Build, due to negative feedback from fans.
- To add her to the Science Club, YandereDev would have to change her appearance.
- Mei Mio and the rest of the Rainbow Six (Except Saki) appear in the town as of October 17th, 2019.
|“||Wow...that's pretty gross...I expected better from Kokona-chan...||”|
— Mei Mio on the Internet.