Yondemasu yo, Azazel-san.

Shows based on Vocaloid originals or involving utaites/producers who are/have been active on Nico Nico Douga (extended to YouTube for newer gens).
While not its own genre, these compositions tend to have a recognisable feel to them.
(Updating as I come across songs, you can poke me to add stuff as well :D)

2nd stack for post-2020 anime debuts: https://myanimelist.net/stacks/26372

Actual Vocaloids:
GUMI ~ Joshikousei no Mudazukai / Agukaru: Play with Ibaraki-hen (cv: Megumi Nakajima)
IA ~ Recorder to Randoseru Mi☆ (cv: Lia)
Miku ~ Akikan / Watamote / Yami Shibai / Black Rock Shooter / Kemurikusa / ALFA-X / Aware! Meisaku / Petit Seka (cv: Saki Fujita)
MEIKA Hime & Mikoto ~ Hakata Mentai! Pirikarako-chan (cv: Kotori Koiwai)
Luka ~ Copihan (cv: Yuu Asakawa)
Meaw (possibly) ~ Honto ni Atta! Reibai Sensei
Go! Go! 575
Zunda Horizon

Luo Tianyi ~ Wan Sheng Jie

Prioritising first appearances/multiple artists bc of 50 limit. For composer entries, the singer is only listed if they're
At some point, I'd have been super hyped for any show with a Vocaloid producer but come late 2010s they've been popping up everywhere :')

*List is roughly sorted by anime based on Vocaloid songs > Male utaites > Female utaites > Producers

MC Female Detectives are quite rare. Here's a collection of them.
Some are less realistic detectives, e.g. in a magic show.
Only the most prevalent anime (meaning an anime not difficult to find) that they are an MC in is included in this list. This excludes sequels and such.

LIGHT SPOILER! Reference, mentions, and depictions of/for sadomasochism or have mean love interest
WARNING: some has romanticization/ eroticization of sexual violence, nonconsensual touching, torture, harassment, physical abuse, bullying.
Keywords: Do-S,Do-M, sadism, masochism, bondage.

Or edgy offensive disturbing anime that have made certain watchers uncomfortable. Definitely recommend to read the reviews + age rating before watching.

Detectives that travel around with an absolute freak just a total freak of a thing. Demons? Gods? Corpses? Puppets? Some kind of freak. The detective can also be weird. Hyouka doesn't count because both protags are equal amount of weird but acceptable little freak. Death note also doesn't count because Ryuk is the one who's followed around by a freak, not L. Please feel free to suggest more. As of now, I've only seen Un-Go and Sakon, both of which are recommendations but Sakon is a lot more tentative of one.