Koi ga Ochitara followed by Koi ga Michitara
It's a really great one!!
If I recall any other great titles I'll swing by again (๑•ㅂ•)و✧
A mixed bag of older seme, younger uke. Some don't have that big of an age gap but since you didn't specify, I placed what I could find here. Some might be...meh like unholy night coz of incest vibes but there ya go.
https://www.mangago.zone/read-manga/unholy_night/
https://www.mangago.zone/read-manga/nakanai_hibari/
https://www.mangago.zone/read-manga/baby_sugar_succubus/
https://www.mangago.zone/read-manga/the_new_employee/
https://www.mangago.zone/read-manga/toumei_na_ai_no_utsuwa/
https://www.mangago.zone/read-manga/tractor_full_of_love/
https://www.mangago.zone/read-manga/the_beast_that_yearns_to_be_tamed/
https://www.mangago.zone/read-manga/unintentional_love_story/
https://www.mangago.zone/read-manga/all_about_lust/
https://www.mangago.zone/read-manga/shinobeba_koi/
https://www.mangago.zone/read-manga/koi_ga_ochitara/
https://www.mangago.zone/read-manga/ore_no_xxx_ga_genki_ga_nai_ken_ni_tsuite/
https://www.mangago.zone/read-manga/love_awakening_x_syndrome/
https://www.mangago.zone/read-manga/pinku_no_pocchi_wo_kakushitaidake/
https://www.mangago.zone/read-manga/kikoeru/
https://www.mangago.zone/read-manga/kokoro_kanda_neko/
https://www.mangago.zone/read-manga/the_lovesick_flower_buds_waiting_for_spring/
https://www.mangago.zone/read-manga/like_a_tidal_wave_from_pheromone_shower/
https://www.mangago.zone/read-manga/kimi_no_sumire/
https://www.mangago.zone/read-manga/koi_wo_suru_tsumori_wa_nakatta/
https://www.mangago.zone/read-manga/the_last_step_on_the_way/
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I hope you find something here to your liking (✷‿✷)
A++++ for effort might read these too.
Hallo hallo haloo i need older seme and then young uke pls like badly