https://www.mangago.me/read-manga/koi_ga_ochitara/
https://www.mangago.me/read-manga/otoko_yamome_mo_hana_ha_saku/
https://www.mangago.me/read-manga/mitsuya_sensei_no_keikakuteki_na_edzuke/
https://www.mangago.me/read-manga/midnight_rain_ctk/
https://www.mangago.me/read-manga/itooshiki_hibi/
https://www.mangago.me/read-manga/suki_ni_nacchau_yo/
https://www.mangago.me/read-manga/kono_ore_ga_ahe_goe_nante_dasu_wake_ga_nai/
https://www.mangago.me/read-manga/oni_to_tengoku/
https://www.mangago.me/read-manga/mujaki_na_wanko_to_nekokaburi/
https://www.mangago.me/read-manga/kore_mo_shigoto_desu/
i don't really have a list of this specifically, but this might just work:
:: Adults in love ! office ver. ✎⋆.࿔*:・
https://www.mangago.me/home/mangalist/2438583/
10 Dance (grown ass adults)
https://www.mangago.me/read-manga/10_dance/
My Father-in-Law Is My Wife (there is at least ONE middle age man lmao, and trust me with this title istg)
https://www.mangago.me/read-manga/my_father_in_law_is_my_wife/
old man or like middle age men yaoi