What chapter is Kakashi gaiden?
It is a Six-foot (or something) based manga, about Kakashi
Hatake as a thirteen year old with Rin (who likes him like Sakura),
and Obito Uchiha (who acts like Naruto).
They also have their Sensei, Minato Namikaze, Naruto's Father
(Naruto doesn't know that),and Kushina Uzumaki's wife.
It explains how Kakashi learned Sharingan not being an Uchiha,
it also explains how Kakashi became a Joinin, and it shows how
Minato Uzumaki, Namikaze was like.
This takes place right after Kakashi, Obito, and Rin take the
Chunin Exams.