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
On 29 July, Mayuzumi reached 10,000 subscribers on his YouTube channel.

On 17 August, Mayuzumi reached 50,000 subscribers on his YouTube channel.

On 10 October, Mayuzumi reached 100,000 subscribers on his YouTube channel.

On 15 October, he revealed he had cataracts in both of his eyes and would have to limit his streaming frequency as they were treated.

2020
On 28 January, Mayuzumi reached 150,000 subscribers on his YouTube channel.

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

On 15 May, Mayuzumi reached 200,000 subscribers on his YouTube channel.

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.

On 24 September, Mayuzumi reached 250,000 subscribers on his YouTube channel.

On 31 December, Mayuzumi reached 300,000 subscribers on his YouTube channel.

2021
On 5 March, Mayuzumi reached 350,000 subscribers on his YouTube channel.

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 28 June, Mayuzumi reached 400,000 subscribers on his YouTube channel.

On 11 September, Mayuzumi reached 450,000 subscribers on his YouTube channel.

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 that he would be absent from NijiQuiz starting from 16 December 2021's episode.

2022
On 27 February, Mayuzumi reached 500,000 subscribers on his YouTube channel.

On 8 May, Mayuzumi made appearance as narrator and guest on his fellow Mescher's group-mates Fuwa Minato and Saegusa Akina's FuwaGusa 3D LIVE stream #ふわぐさ3Dライブ titled "Dream that came true" (叶えたかった夢, Kanaetakatta Yume) on Minato's channel.

Retirement
On 2 July, Mayuzumi announced that on his 3rd debut anniversary on 28 July 2022, along with the end of his contract with NIJISANJI, he would be also graduating.
 * He explained the reason for his graduation through the graduation announcement stream that around November 2021 he was approached by ANYCOLOR management to talk about the future plan, but the plan suggested to him was not aligned with the direction of ideas and plans he projected back in August 2021; after long discussions and proposals up until February 2022, and with no common ground found, he decided to graduate from ANYCOLOR and NIJISANJI. Along with his graduation, while his YouTube channel and Twitter account would be still available publicly, some archives would be made unlisted (they would be still viewable but not on the top page of his channel).
 * Up until the day of his graduation, he would be either streaming or posting videos everyday.
 * On the same day, Mayuzumi reached 550,000 subscribers on his YouTube channel.

On 13 July, Mayuzumi reached 600,000 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 Minecraft 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".
 * On 5 March 2021, he tweeted that he doesn't officially recommend the use of this fan name or his oshi mark anymore. So it is fine for fans to use whatever they would like instead.
 * 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.
 * "MoonlightBlossoms" 「月下の桜」 - Kai, Fuwa Minato, Hoshikawa Sara, Ibrahim, Shiina Yuika and Gundo Mirei
 * "Violence Takeda"「バイオレンス武田」 - Kai, Kuzuha and Kanae

Trivia

 * Color: #086776
 * Mayuzumi has a mascot called Uchina Irokichirou 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. He has mentioned that he doesn't have a sense of rhythm and seems to be nervous about the expectations put into his singing skills.
 * 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.
 * Mayuzumi's channel is only monetized to a minimum. He usually doesn't have Super Chats on for his streams nor does he have a membership available for his channel. When he does switch on Super Chats for a stream (usually special occasions like anniversary streams), he usually is showered in them while fans still can.
 * When asked by Tamaki in a collab stream as to why he doesn't switch on SC, he mentioned that he finds it bothersome as they take up more space in the chat column, which would make it harder to read the rest of the chat. It also boosts his Voice Packs, which fans buy instead as a means to support him monetarily.
 * He has pondered in a stream about opening membership if he could put the fee at 1M yen in an attempt to raise the price so high that no one would dare to purchase the membership. When asked what he would do if someone would actually pay that sum, he replied that he would run away.

Media

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

Twitter hashtags

 * #ライブハック - Stream talk
 * #灰画 - Fan art
 * #黛使用済み - Fan art (NSFW)
 * #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