you've got good taste! (you may have already ready these are they're pretty well known but I thought I'd list them anyway)
"Beware the Villainess!"
"The Villainess Lives Twice"
"The Monster Duchess and Contract Princess"
"The Villainess Reverses the Hourglass"
"My Next Life as a Villainess: All Routes Lead to Doom!" (also has an anime now)
"The Villainess is a Marionette"
https://www.mangago.me/read-manga/even_though_she_is_a_weak_max_daughter_she_has_taken_a_bet_from_a_shrewd_fianc_e/
https://www.mangago.me/read-manga/the_male_lead_monster_lives_under_my_bed/
https://www.mangago.me/read-manga/i_became_the_wife_of_the_male_lead_bored_corona_kids_version/
https://www.mangago.me/read-manga/meng_shi_zai_shang/
https://www.mangago.me/read-manga/marriage_substitute/
https://www.mangago.me/read-manga/the_result_of_being_reincarnated_is_having_a_master_servant_relationship_with_the_yandere_love_interest/
https://www.mangago.me/read-manga/recording_hall/
https://www.mangago.me/read-manga/lucia/
https://www.mangago.me/read-manga/the_villainess_want_to_marry_a_commoner/
https://www.mangago.me/read-manga/i_raised_an_obsessive_servant/
https://www.mangago.me/read-manga/kitsch_wedding/
https://www.mangago.me/read-manga/it_seems_like_i_got_reincarnated_into_the_world_of_a_yandere_otome_game/
https://www.mangago.me/read-manga/raising_the_enemy_only_brings_trouble/
https://www.mangago.me/read-manga/i_became_the_villain_s_trainer/
https://www.mangago.me/read-manga/i_m_a_banished_villainess_but_i_m_accompanied_by_a_fluffy_creature_my_peaceful_life_starts/
https://www.mangago.me/read-manga/i_ll_do_that_marriage/
https://www.mangago.me/read-manga/i_m_a_stepmother_but_my_daughter_is_just_too_cute/
https://www.mangago.me/read-manga/don_t_trust_the_female_lead/
Thank yooou (▰˘◡˘▰)
Thank yooou (๑•ㅂ•)و✧
You're welcome. Have fun reading ヾ(❀╹◡╹)ﾉ~
I am currently searching for manga/manhwa/webtoon where the ML has an obsession of variant extents with the FL but the FL is not aware (or not fully aware to the extent of the obsession) Lately the few I've read have been isekai where they start out as children and you watch them grow together as the attachment starts. Two examples of what i'm looking for that come to mind are:
https://www.mangago.me/read-manga/the_villainess_is_oblivious_to_the_prince_s_true_doting_nature/
https://www.mangago.me/read-manga/jishou_akuyaku_reijou_na_konyakusha_no_kansatsu_kiroku/
I know ive read a few more but these are the only two I can think of as examples rn