Name of these two Doujinshi characters and source?

Artist : Usa
https://e-hentai.org/s/145120fcaf/2023481-761
https://e-hentai.org/s/d0d7eea184/2023481-647

I'm not sure if it's a Doujinshi I think it's a request for the artist made by a fan

Artist: https://twitter.com/usa18_/media

https://twitter.com/usa18_/status/1293511173233676288/photo/2

https://twitter.com/usa18_/status/1195319251222974464/photo/1

Artist : Usa
https://e-hentai.org/s/145120fcaf/2023481-761
https://e-hentai.org/s/d0d7eea184/2023481-647