"Glad to see you! I'm Ai Yazawa! Thank you very much for having bought Nana 7.8! I guess some of you are wondering, 7.8? But what does that mean? You will understand by reading the volume. If you are unable yet to understand, re-read the series from the beginning. Then, re-read this book again for fun! And maybe you will have the desire to read again series from number one!"
Nana 7.8 is a fanbook by Ai Yazawa on March 14, 2003. The volumes fit in between volumes 7 and 8 of Nana, hence the 7.8. The book includes full color pages, character statistics, and an interview from Ai Yazawa.
In the bonus pages of volume 8, Junko closes her bar down because of the party in volume 7.8.