In The Wolverine, Kenuichio Harada is the head of a band of ninjas that has defended the Yashida family for 700 years. In the early part of the film, he uses his skills in a failed effort to protect Mariko Yashida from kidnapping by yakuza. Later, he uses his skills to capture Wolverine, who was wanted by Mariko's grandfather so that he could steal the mutant's healing factor.
In the climactic battle, Harada suddenly switches sides, attacking the elder Yashida in defense of Wolverine. Why? How are the interests of either member of the Yashida clan advanced by this?