I will try to group the related works together
A)
https://www.mangago.zone/read-manga/love_stage/
https://www.mangago.zone/read-manga/back_stage/
B)
https://www.mangago.zone/read-manga/kuroneko_kareshi_no_asobikata/
“Series Chronological Order
1) Kuroneko Kareshi no Asobikata
2) Kuroneko Kareshi no Amaekata
3) Kuroneko Kareshi no Nakasekata
4) Kuroneko Kareshi no Aishikata
5) Kuroneko Kareshi no Afurekata
6) Kuroneko Kareshi no Ouji Sama --> Extra story in Kuroneko Kareshi no Afurekata vol 3
Also:
Nekoka Danshi no Shitsukekata (Adapted From)
Nekoka Kareshi no Ayashikata (semi prequel)
Fukigen Kareshi no Nadamekata (Spin-Off)
Fukigen Kareshi no Saraikata (Spin-Off)“
C)
https://www.mangago.zone/read-manga/pendulum_kemonohito_omegaverse/
“1) Pendulum: Kemonohito Omegaverse
2) Remnant: Jujin Omegaverse
3)Petit Mignon
4)Cuddle: Juujin Omegaverse”
D)
https://www.mangago.zone/read-manga/happy_yarou_wedding/
“ 1. Happy Yarou Wedding
2. Utsukushiki Kemonotachi.
3. ...Virgin Love.
4. Toriko ni Natta Kemono
5. Junai no Seinen
6. Kemono wa Ai de, Iyasareru.
7. Playboy Amour
- Romance no Kaori
8. Oboreru Kemono no Koibito.
9. Men's Love
10. Aikata
11. Ueta Aikata
12. Amaeta Kemono no Shitsukekata
13. Torawareta Amai Kemonotachi
14. Aikata no Aishikata
15. - Kemono no Marking
16. - Erotic ni Kojiakete
17. - Kemono na Kouketsu Egoist
18. - Kedakaki Kemono no Territory”
E)
https://www.mangago.zone/read-manga/hanamuko_san/
https://www.mangago.zone/read-manga/hanayome_kun/
F)
https://www.mangago.zone/read-manga/akai_ito_no_shikkou_yuuyo/
https://www.mangago.zone/read-manga/kanawanu_koi_no_musubikata/
https://www.mangago.zone/read-manga/tsunaida_koi_no_kanaekata/
G)
https://www.mangago.zone/read-manga/kare_no_tokubetsu_na_kare/
https://www.mangago.zone/read-manga/kare_to_kare_no_ijiwaru_na_kyori/
H)
https://www.mangago.zone/read-manga/bi_no_isu/
“1. Aoiro Keiyaku (Sep 2006 to ?) | 1 Volume 5 Chapters - Side Story
2. Bi no Isu (Aug 10, 2008) | 1 Volume 5 Chapters - Prequel
3. ≠ (Oct 28, 2009 to Aug 27, 2011) | 2 Volumes 11 Chapters
4. Pink Gold (Aug 28, 2012 to ?) | ? Volume ? Chapter - Other
5. Bi no Kyoujin (Oct 27, 2012 to Oct 28, 2015) | 2 Volumes 14 Chapters - Sequel / Other / Prequel
6. Bi no Kyoujin: X Side (Jun 28, 2013 to Jun 28, 2016) | 1 Volume 8 Chapters - Other
7. Smoke: Bi no Kyoujin 3 (Aug 27, 2016 to Jun 28, 2017) | 1 Volume 7 Chapters - Sequel”
I)
https://www.mangago.zone/read-manga/interval_zero/
https://www.mangago.zone/read-manga/junketsu_drop/
J)
https://www.mangago.zone/home/mangalist/207246
1. Warui Koto Shitai (I Want To Be Naughty!)
2. Warui ko demo ii?
3. Kirai ja Naikedo (I Don't Dislike You)
4. Koi ja nai kedo
5. Warui Koto Bakkashite Gomennasai (spin-off)
6. Warui Yatsu Demo Ii
7. Mujihi Na Otoko
8. Warui Koibito ja Dame?
9. Kare Ja Nai Kedo
10. Mujihi Na Anata
11. Sunao Ja Nai Kedo
12. Mujihi Na Karada
13. Warui Ouji Demo Suki
14. Shouwaru Ookami ga Koi wo Shita Rashii
15. Masato-Sama no Urei Aru Nichijou ~to, Kare wo Aisuru Monotachi~
16. Himitsu Ja nai kedo
K)
https://www.mangago.zone/read-manga/kono_ore_ga_omae_nanka_suki_na_wakenai/
https://www.mangago.zone/read-manga/gosan_no_heart/
L)
https://www.mangago.zone/read-manga/love_is_an_illusion/
https://www.mangago.zone/read-manga/love_is_fantasy_the_queen/
M)
https://www.mangago.zone/read-manga/renai_nante_yurushimasen/
1)Renai Nante Yurushimasen!
2) Netsuai Nante Ariemasen!
3) Dekiai nante mitomemasen
4) Saiai Nante Yuzurimasen
There's a lot of story that Co exist in the same dimensions. For example The Third Ending and Hello Again or Lily and Lala series.
Is there any more story like?
Specially in shoujo genre