Milky Holmes

Milky Holmes are
- Suzuko Mimori as Sherlock Shellinford,
- Sora Tokui as Nero Yuzurizaki,
- Mikoi Sasaki as Hercules Barton, and
- Izumi Kitta as Cordelia Glauca.

They are a seiyuu unit from/for the anime Tantei Opera Milky Holmes. When performing a live, each member wears a certain cosplay to look like her 2D counterpart from the anime.

Company profile: https://hibiki-cast.jp/hibiki_f/milky-holmes/

The same members also did Glitter*Green, which released only one single Don't be afraid! on November 21, 2018.
https://bushiroad-music.com/artists/glittergreen