Haloo

https://www.mangago.me/read-manga/love_in_hell_jujucat/

Formless
Love in Hell
Warning: both of these are super toxic with major red flags but thats what comes to mind

Let Me Love You ( https://www.mangago.me/read-manga/stalk_in_love/) has a plot exactly like the one you're looking for.

https://www.mangago.me/read-manga/stalker_x_stalker_kadiro/
This is more of both stalker but ML was like ohh me too. This might not match to what you want but that what I know

Have you read the BEST new-gen DARK FANTASY, ACTION SHOUNEN MANGA of the 2020s, the peak of human literature, Kagurabachi? If you're looking for a story with a more slow-burning pacing and world-building, but masterfully-written plot, realistically written and interesting characters with great designs, GORGEOUS ART that evolves with each new chapter, MOVIE-LIKE fighting choreography, BEAUTIFUL panelling and composition and NO ROMANCE, ZERO FANSERVICE AND ABSOLUTELY NO SEXUALISATION, ESPECIALLY OF IT'S FEMALE CAST!! OH ALSO IMPORTANT MENTION; DON'T DROP THIS AT CHAPTER 58 (IYKYK), TRUST THE PROCESS OF HOKAZONO-SENSEI'S GENIUS!!  GO READ IT NOW!!!

https://www.mangago.me/read-manga/kagurabachi/ (PEAK FICTION)

Also these mangas are great, too:
https://www.mangago.me/read-manga/gokurakugai/
https://www.mangago.me/read-manga/tokyo_aliens/
https://www.mangago.me/read-manga/gachiakuta/
https://www.mangago.me/read-manga/galaxias/
https://www.mangago.me/read-manga/centuria/
https://www.mangago.me/read-manga/witchriv/
https://www.mangago.me/read-manga/madan_no_ichi/
https://www.mangago.me/read-manga/tongari_boushi_no_atelier/
https://www.mangago.me/read-manga/night_light_hounds/

Apocalypse

Mosquito wars

I'm here to spead and proclaim peak:
Eternally Regressing Knight
Reborn as the Enemy Prince (more political but urgh I swear it's so good)

Thank you guys for the recommendations!!