NANA is the best anime i ever saw, even tho its from the 2006, they understand very good the adult life and all about it, relationships, while hachi starts being so immature, while the episodes go on, she starts to be more mature even tho she has a hard love life. Nana instead is a character with her punk personality and looks, i rlly love her, i even have the same guitar or one simillar, i rlly like how she gave up the love of her life for her dream : being a famous singer with her band even tho she met Ren once again, its sad he died on the manga bc i rlly love ren too.
In conclusion, i think Nana is a pretty good anime to watch in your adult life, maybe when you grow up you could understand it way better.