KaiMei

KaiMei is the het ship between Meiko and Kaito from the Vocaloid and Project SEKAI fandom.

Canon
MEIKO and KAITO are characters from the vocal synthesizer application VOCALOID. They do not have any official relationship, personalities, or backgrounds. Most of their characterization is left to songs and semi-official materials such as video games. In most user-made songs, they are usually seen together in some fashion, due to the fact that they were the first Vocaloid characters developed by YAMAHA and distributed Crypton. They were also the first Japanese female and male voices to released on VOCALOID period.

Project DIVA Series
Kaito and Meiko appear together in the Project DIVA series of rhythm games by SEGA. They are often in close proximity, such as in Project DIVA F 's opening sequence where they're shown playing music together when Miku finds them. They also have two PVs together over the course of the series, "Tsugai Kogarashi" and "on the rocks", where they duet. In Tsugai Kogarashi, Kaito and Meiko are portrayed as a pair of winter winds entering the season together, and Kaito is shown taking Meiko's hand along a bridge in a Japanese temple along with dancing in tandem with her. In "on the rocks", they're depicted as a lounge singer and a piano player performing in a bar, seemingly wooing each other considering the sensual lyrics.

Project SEKAI
Kaito and Meiko also appear together in Project SEKAI: Colorful Stage!, a mobile game featuring the Crypton Vocaloid characters alongside original characters inhabiting a personal world called a "SEKAI". Kaito and Meiko, so far, have appeared as a pair in the Classroom, Wonderland, and Street Sekais, each with their own take on their relationship. In the Classroom Sekai, Meiko and Kaito are bandmates, with Kaito being a shy young man who prefers to play music to express his feelings and Meiko being a passionate and caring drummer who tends to look after the rest of the band. In the Wonderland Sekai, Kaito is a ringmaster-like performer with Meiko being one of his assistants, and he's seen partnering with her in setting up shows inside the SEKAI. In the Street Sekai, Meiko is a levelheaded coffeeshop owner, while Kaito is a carefree DJ who visits the cafe often to see her - Meiko is depicted as chiding him slightly for his more airheaded moments.

Songs
Meiko and Kaito have several songs depicting them in a romantic manner, and just as many where they simply shown as inseparable, such as in "Alice in NY" or "Bad End Night" where they're depicted together. They are also a very popular pair for making covers, as they are meant to be somewhat complementary voices due to their status as the first Japanese female/male voicebank pair. Their most popular duet songs are Tsugai Kogarashi and On the rocks.

Fanon
KaiMei is one of the oldest and most popular straight pairings within the Vocaloid fandom. Part of this is due to their complementary color schemes and voice qualities (Meiko being red and having a low feminine voice while Kaito is blue and has a higher-pitched masculine voice) and the popular interpretation in the fandom of them being the "mom" and "dad" figures to the rest of the Crypton characters (who are like their "kids"). Not to mention, many find the ship appealing in a similar way to RinLen for the fact that Meiko and Kaito were designed to complement each other, making them "made for each other" in a way. It's also popular to give them opposing personality traits to accomodate such headcanons, such as making Meiko more brash and snarky and Kaito being goofy and optimistic. However, some have negative feelings towards the ship due its prevelance amongst fans, or disliking it for some of the more unhealthy portrayals such as Meiko using Kaito as a punching bag.

It is the most popular Meiko ship and one of Kaito's more popular one, their main rival ships are KaiMiku, Kailen and GakuKai, KaiMei, being the most popular on Pixiv and AO3, although it isn't the same in all pages or countries. The ship has +155 works on AO3 and +4700 works on Pixiv, being one of the most popular ships in the fandom along with RinLen and Negitoro

Fandom
FAN FICTION

ART
 * カイメイ tag on Pixiv