Twenty-six "Naruto" light novels, the first nine written by Masatoshi Kusakabe, have been published in Japan. Of these, the first two have been released in English in North America. The first adapted novel, "Naruto: Innocent Heart, Demonic Blood" (2002), retells a Team 7 mission in which they encounter the assassins Zabuza and Haku; the second, "Naruto: Mission: Protect the Waterfall Village!" (2003) was based on the second OVA of the anime. Viz has also published 16 chapter books written by Tracey West with illustrations from the manga. Unlike the series, these books were aimed at children ages seven to ten.