The two main character has the same name,the same age,come from the country and going to tokyo for the first time.The cool and gothic one is Nana(the other is Nana too but.....),the second who's her total opposit is called hachi by her friends in the manga.
Hachi followed her boyfriend to tokyo,at least in theory.
For Nana,they didn't say anything in ep 1 so I am sorry but it's a spoiler.