Summary : Nana Komatsu has a habit of falling in love at first sight all the time, and depending on other people to help her. When her friends, and then her boyfriend, leave for Tokyo, she decides to join them a year later after having saved enough money at the age of 20. Nan Osaki is a punk singer who wants to make it big with her band BLAST (Black stones). Her and her boyfriend Ren, who is also the bassist in BLAST, have been together since she was 16. When Ren is offered a chance to be the band Trapnest in Tokyo, Nana decides to stay and continue with her band BLAST and try to make it big. Plus, she is way too ambitious to just be a rockstar's girlfriend. Eventually, she leaves for Tokyo to pursue her musical career, at the age of 20.
The two Nanas meet on a train by chance, both on their way to Tokyo. After a string of coincidences, they come to live together in an apartment numbered 707 (nana means "seven" in Japanese). Despite having contrasting personalities and ideals, the Nanas like and respect each other a great deal.
Nana Osaki gives Nana Komatsu the nickname Hachi (after Hachikō, because she is weak-willed and has characteristics that resemble a puppy, and also as a joke since hachi means "eight" in Japanese).
While BLAST begins to gain popularity at live gigs, the two Nanas' face many other issues together, especially in the areas of friendship and romance. The story of Nana revolves heavily around the romance and relationships of the two characters as one seeks fame and recognition while the other seeks love and happiness...
My review : If you don't like an anime that'll bring you to tears in almost every episode...then this is not for you. It's sort of mature (No ecchi but, you can hint some yuri nothing explicit though!) The plot is very good. From the first episode to the 47th (Which is the last.) you will be HOOKED. The characters develop very slowly, but sure enough by the end you will be like NOW I SEE. The OP & ED songs are really good too! My favorite opening happens to be "Wish" a Trapnest song. (: (It's also on my ipod :D) But, it's not all about Drama. there are plenty of parts where you will be laughing your ass off.

And as for romance you almost feel for hachi (Nana K or if you don't know the more girlier Nana) and her situation. involving the opposite sex. (Can't tell you what all goes on, SORRY xD) Nana O's relationship with Ren is almost amazing (Still won't tell. just WATCH!). The animation is nothing special and at first sight looks a little daunting.
Also, there are soo many freakin' twists in the anime it's RIDICULOUS.But, you'll love them.No filler epis either. (which i like.) So you don't have to worry about it going off topic. (: Now for the ending..it's sad and beautiful at the same time. There are plenty of things i wish would've happened, but if they did it just wouldn't be the same..... Remember this: 707 has a special meaning....
All in all : It's a really great anime. One of the best I've seen like forever. I recommend this for anyone who like a well developed storyline, easy to relate to characters, and awesome music. GO WATCH.