The 23-year-old is currently in the middle of a two-year loan to Borussia Monchengladbach, but he has admitted that talks have taken place with the Naples outfit regarding a transfer.
"There is contact with Napoli. The offer is interesting, especially because Rafael Benitez is the manager and he is a great coach," Kramer told Bild.
"At the moment I cannot say anything else. I could go back to Borussia - there are many possibilities."
Kramer was part of the Germany squad that won the World Cup this summer.