(I adopted a ton of these from this VOCALOID headcanon blog I found)
-Meiko, Haku, and Tonio all go out drinking together.
-Meiko has a FREAKISH amount of alcohol tolerance and drinks for the flavor.
-Tonio has an average amount of tolerance and drinks because he thinks no one likes him.
-Haku has a very low amount of tolerance and drinks because at first she wanted to get closer to Meiko (she had a tiny crush on her that died off) but now it has become a habit she cannot stop.
-Neru only became friends with Haku to get closer to Haku's brother Dell (he was the closest she could get to Len)...but now she's falling in love with Haku.
-Meiko and Luka are best friends (obviously.) I don't mind seeing them paired romantically too....
-Rin and Len read a fanfiction once. They couldn't sleep for DAYS.
-Rin has a huge crush on Miku and Len likes teasing her about it.
-It's very obvious that Yukari and IA have feelings for each other, but they're both too shy to do anything about it.
-Lily and CUL both love to sing rock songs and thus are best friends.
-Gumi has a huge crush on Lily. CUL looks up to her. Gakupo thinks she's a bad influence on everyone.
-Once Kiyoteru and Miki found out that Yuki was being raised by an abusive family, they adopted her.
-Len is Gumi's best friend and wingman, and Gakupo watches them like a hawk out of older brother instinct even though they only love each other platonically. They get mistaken for a couple all the time, which irks them.
-Piko and Rin are also good friends. Sort of an opposites attract thing.
-Yukari doesn't only like chainsaws, she keeps a whole range of weapons and keep them under her magical hoodie.
-Teto, Rin, Miku, and Gumi are all hardcore fujoshis. Teto's OTP is Ted x Rook, Miku's is Akaito x Dell, and Gumi and Rin share the OTP of Len x Piko.
-Yuuma, Mizki ,Gakupo, Luka, and the UTAU Nagone Mako are all in a little fencing club together.Yuuma and Gakupo have a teacher-student relationship and respect each other. Luka and Mako don't understand that there is such a thing as a friendly fight and try to kill one another every day. Mizki just sits there drinking her tea all ladylike but she could take them all on and win if she wanted.
-Iroha is one of the only people who knows about Ice Mountain and regularly blackmails poor Kiyo into singing for her.
-Surprisingly, Rin and Tei are good friends.
-Clara is Meiko's Spanish cousin, and they like to go out drinking together while Bruno and Kaito patiently wait for them to come home.
-Piko and Flower are siblings and YANHE is their Chinese cousin.
