During a "gaiden" on his past, Kakashi is revealed to been trained by Naruto's father during the Third Great Ninja War and obtained his Sharingan eye from one of his teammates, Obito Uchiha.
During a "gaiden" on his past, Kakashi is revealed to been trained by Minato Namikaze during the Third Great Ninja War. He later obtains a Sharingan eye from one of his teammates, Obito Uchiha.