I'm looking for a romance manga, it can be Seinen or Shoujo, what i want for is, it's drama should be somewhat "realistic" , it would be nice if the art is decent.

Ps. I'm not really into "too deep" drama.

Ashita no Ousama
Bara no Tame ni
Cat Street
Atsui Hibi
Bus Hashiru
Watashitachi no Shiawase na Jikan
Diamond Life
Game Over
Hana no Namae

Not sure if you would like these but you can give it a try:
Hotarubi no Mori e
Emma

Kakafukaka
watashitachi wa douka shiteiru

These are shoujo:
Mars
Bokura ga ita
Sand Chronicles

Kareshi Kanojo no Jijou
Sensei!

"We can not resort to simplistic or extreme solutions which substitute myths for common sense." ― Jimmy Carter

You can try Kimi wa Houkago Insomnia, it has an atmosphere that drama can appear at any moment.
I also second Mars, even if it is a bit melodramatic.