any bls where the mcs are in an established relationship before the story begins?

Black or White

https://www.mangago.zone/read-manga/day_off/
https://www.mangago.zone/read-manga/call_me_dior_zhang/
https://www.mangago.zone/read-manga/the_most_ordinary_relationship/
https://www.mangago.zone/read-manga/hiyoko_to_yoru_to_yuenchi/
https://www.mangago.zone/read-manga/oni_to_tengoku_kyuu/
https://www.mangago.zone/read-manga/boku_no_papa_to_papa_no_hanashi/
https://www.mangago.zone/read-manga/shiawase_gohan_maki_to_hanazawa/
https://www.mangago.zone/read-manga/loss_time_ni_hanamuke_o/
https://www.mangago.zone/read-manga/our_not_so_lonely_planet_travel_guide/
https://www.mangago.zone/read-manga/wareta_cup_wo_modosu_ni_wa/
https://www.mangago.zone/read-manga/papa_x_papa_to_de_sorezore_yattemasu/
https://www.mangago.zone/read-manga/neko_x_neko/
https://www.mangago.zone/read-manga/shima_chanchi_no_tsugaijijou/
https://www.mangago.zone/read-manga/family_now_and_forever/
https://www.mangago.zone/read-manga/kowagaranai_de_soba_ni_ite/
https://www.mangago.zone/read-manga/haru_to_natsu_to_nacchan_to_aki_to_fuyu_to_boku/
https://www.mangago.zone/read-manga/itooshiki_hibi/
https://www.mangago.zone/read-manga/kawa_ni_sazanami/
https://www.mangago.zone/read-manga/motoyan_papa_to_hitsuji_sensei_yotsuba/
https://www.mangago.zone/read-manga/tonari_no_ren_kun_wa_chotto_kowai/

Have you read any of these? (≧∀≦)