Nana was, I must admit, relatively realistic for a Manga.

Firstly:

We meet Nana#1, later nicknamed Hachikō, as the story begins, a dumb-ass of a chick, more like a hopeless case of the human race.
That's either: WAY too horny or must have been high on SOMETHING for most of her life.
Falling in 'love at first sight' seems to be her strongest skill, as well as 'judging a book by its cover' and inevitably, is a pro at being the victim of breakups. Though sometimes she is cute, she can be a major headache for readers and characters alike.

Then we meet Nana#2, nicknamed the Dark Priestess by Nana#1's bestfriend, and seems to be the trump card of Black Stones, her band, and is generally a wild kind of chick, that at times has a heart made of gold and is a whole lotta fun when she is drunk.

And through circumstances these two Nana's meet and so is born the plot.

The writer has built strong, flexible personalities that flow through their story. More than the actual story, I liked the characters. Everyone of them had their own idiosyncrasies, their own habits, their own style and most importantly, their own life; in other words, realism.

The art was unique to the story and definitely, the artist infused their own style into the art and for that, this Manga is on a different level to most Mangas' and Manhwas' because of its originality. For the illustrator not to follow the mainstream style of art that most stories use is a great feat within itself and keen readers appreciate the effort; a lot.

Overall, the story does get slow but if you suck it up; you'll find that the story is not as over-rated as you thought.