Similar Recs?

Waterside night
https://www.mangago.me/read-manga/heesu_in_class_2/
https://www.mangago.me/read-manga/to_make_a_delicious_omega_squeak/
https://www.mangago.me/read-manga/ore_sama_na_doukyuusei_no_kenzoku_ni_narimashita/

Have you read nevermore? It's not exactly a possessive main lead but the vibe of the plot matches

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

Try this
https://www.mangago.me/read-manga/b_class_guide/

I recommend other works from the same artist. They give similar vibes.

Honestly Park Hanhoo's Manager is one of my favourites, so here are my other favourites (they might not be exactly similar, but maybe you will like some of them):

Dance with the Devil
https://www.mangago.me/read-manga/dancing_with_the_devil/

Saezuru Tori wa Habatakanai
https://www.mangago.me/read-manga/saezuru_tori_wa_habatakanai/

Sankaku Mado no Sotogawa wa Yoru - not exactly romance, but deep connection
https://www.mangago.me/read-manga/sankaku_mado_no_sotogawa_wa_yoru/

Murderer Llewellyn's enchanting dinner invitation - very possessive
https://www.mangago.me/read-manga/murderer_llewellyn_s_enchanting_dinner_invitation/

Kill the Lights - possessive
https://www.mangago.me/read-manga/kill_the_lights/


Its honestly hard for me to find something similar to the Park Hanhoo's Manager, cuz it's such a unique plot and vibe. The closest are other works of the artist imo