Mayuzumi Kai

Mayuzumi Kai (黛灰) is a male Japanese Virtual YouTuber affiliated with NIJISANJI. He debuted alongside Ars Almal and Aiba Uiha, known as the trio "Blues" (ぶるーず).

Profile
An aloof and talented white-hat hacker who began livestreaming as part of an undercover investigation. He rarely goes outside and orders everything online.

Personality
Cool-headed and reserved, Mayuzumi is known for his monotone way of speaking and his blunt and sarcastic humour. He will often speak casually to his seniors instead of using polite speech, much to their annoyance. Mayuzumi will often suddenly act out of character through exaggerated voice acting or peculiar video editing; most famously, at the suggestion of his viewers he completely reversed his personality and acted in an energetic and polite manner.

As shown through his frequent collab and call-in livestreams, he gets on well with many livers including those outside of NIJISANJI such as Natsuiro Matsuri from hololive. , and his own illustrator Ichijiku.

Due to his quiet personality, others often become excited if they are able to make him laugh.

Aside from the usual VTuber game titles, he most often plays indie games.

Background
Mayuzumi made his YouTube debut on 29 July 2019.

2019
In October he revealed he had cataracts in both of his eyes and would have to limit his streaming frequency as they were treated.

2020
In February he resumed regular streaming after recovering from surgery to remove the cataracts.

On 3 July, Mayuzumi announced he would be in his official 3D model debut on 10 July. He unveiled his official 3D model on 10 July as scheduled.

2021
On 16 June, Mayuzumi broadcasted a lore video in the real-world Akihabara. In this video, he acknowledged his own nature as a fictional character and speculated on the relationship between his world and the real world.

On 3 December, Mayuzumi announced that he decided to take a break from streaming at least until February 2022. Later on a stream, he mentioned that the reason was because he had been developing mild symptoms of depression and visibly worsening. The symptoms had affected his health such as making it harder for him to concentrate, experiencing insomnia, and developing fevers, to the point of him needing to take short breaks previously. However, he would still appear on official NIJISANJI channel and regular shows, as well as sponsorship events he had planned prior to the decision.
 * On 14 December, Mayuzumi gave an updated announcement that NIJISANJI management had stopped him from continuing his appearance in NIJISANJI official programs and regular shows including NijiQuiz in concern to his health; and he will be absent from NijiQuiz starting from 16 December 2021's episode.

2022
On 28 February, Mayuzumi reached 500,000 subscribers on his YouTube channel.

2021

 * On 18 September, he participated in Autumn Minecraft Premium Stage ~Big Gathering of Game Streamers~ (秋のマイクラ プレミアム ステージ 〜ゲームストリーマー大集合！〜) as Team C along with Kuzuha, Kanae, Fuwa Minato, Ibrahim, and Ex Albio. The team won 1st place on 1st stage.

2022

 * On 27 February, Mayuzumi participated in the NIJISANJI VALORANT Custom event organized by Lauren Iroas and Naraka as team "AmaEbi Daifuku" along with Shiina Yuika, Ex Albio, Ars Almal, and Amamiya Kokoro.
 * On 4 April, Mayuzumi participated in the Mycla Versus - The Battle of the Ender Dragon (マイクラバーサス 〜 エンダードラゴン対抗戦) live event hosted by the official Minecraft Japan as part of Team D alongside Belmond Banderas, Genzuki Tojiro, Sakura Ritsuki, and Kitakoji Hisui.

Fans

 * The name for his fans is "ListeNerds".
 * He begins livestreams with his famous "Do-mo" (どーも lit. Hello) catchphrase.

Relationships

 * "Blues" 「ぶるーず」 - Kai, Aiba Uiha, and Ars Almal. They are debut-mates.
 * "Mescher's" 「メッシャーズ」 Kai, Saegusa Akina, and Fuwa Minato. These three all have highlights in their hair.
 * "Natsumatsurikkai" 「ナツまつりっかい」 - Kai, Natsuiro Matsuri, Kuroki Natsume, and Rikka.

Trivia

 * Color: #086776
 * Mayuzumi has a mascot called Iroki Shirou who is based on the color of his inner hair. Iroshi Shirou is a turquoise strand of hair wearing a happi, traditional Japanese festival wear, and a headband. He speaks in an old Edo speech/dialect, and has very loud and energetic but masculine and old-fashioned mannerisms.
 * His favourite anime is Serial Experiments Lain
 * He is weak to horror games.
 * He uses "X" in his Twitter username as the Greek letter "χ" can be pronounced "Kai".
 * As "χ" can also be pronounced "Chi", he uses it in his channel header for the phrase "Mayuzumi χannel"
 * He wrote the lyrics to Aiba Uiha's first original song, "Yume e Mukatte Maenarae!".
 * He typically avoids singing. On 22 August 2021, Aiba Uiha premiered what appeared to be a duet cover of Turing Love with Mayuzumi, but instead of Mayuzumi himself singing, the cover featured a voice synthesizer that resembled his voice.
 * He is left handed

Media

 * 黛灰/Kai Mayuzumi【にじさんじ】 - YouTube channel
 * Mayuzumi's corporate profile on the official NIJISANJI website
 * @mayuzumi_X - Twitter account
 * @BBash_Shell - Twitter Sub account

Twitter hashtags

 * #ライブハック - Stream talk
 * #灰画 - Fan art
 * #黛声 - Commentary on released voice dramas
 * #灰ジェスト - Video clips

Further readings

 * 黛灰 (まゆずみかい) - Unofficial NIJISANJI wiki
 * 黛灰 - Nicovideo Encyclopedia
 * 黛灰 - Pixiv Encyclopedia
 * 黛灰 - Moegirl Encyclopedia