What I am looking for is pretty much just romance with the main male interest having long hair. I don't really care about the genre other than no horror or/and psychological

Horimiya

Unfortunately, he cuts his hair later.

I hope you like fantasy/historical:

Chang Ge Xing (his hair is gorgeous...)
Saver
Suijin no Hanayome
Yume no Moribito
Ashi-Girl
Versailles no Bara
Kami-sama Hajimemashita (his hair changes between long and short at various times)
Kanata Kara

Inuyasha

literally any historical romance manga ever, esp the chinese ones.
on the top of my head i can remember:

shen yi di nu (medical doctor goes back in time and enters body of bullied female and basically gets revenge whith the help of her fiance the 9th prince who is hooooot)

ugly woman's harem code (after seven yrs of marriage she is killed by husband along with their unborn child and is reborn to before she met him and basically want to get revenge but ends up falling for some one else)

my dear cold blooded king (this cannot be summerised into words, it is ART, the visuals are amazing the guys are all so good looking, you will binge read this its so good)

i know a lot of manga similar to the first one (the idea of a stronger female being reborn from modern times into an ancient time transfering into the body of a weak and bullied female and then eventually get revenge for them as well and mainly falling in love with a powerful male figure) if your interested then tell me cuz there will be plenty of long haired fellas 😛

Mars It's just... He is the most beautiful male lead i've ever seen so far. Story is also good.
Tsubaki-chou Lonely Planet

If you read webtoons there are some good ones:
Little Rain - You can read it in line webtoon, discover section
Midnight Poppy Land - discover, line webtoon
Purple Hycanith - currently my favorite webtoon. it's. just. amazing.

Sabaku no Harem