Quick recap
The fifth Shippuden movie. Accused of attacking the Raikage, Naruto is locked up in Hōzuki Castle, a maximum-security prison. The warden, Mui, seals his chakra. A guard named Ryūzetsu reveals that Mui framed him to exploit the Fox's chakra. His plan is to open a legendary box that holds his son, Muku. When the box opens, the boy comes back possessed by Satori, a demon that tears through the castle. Mui sacrifices himself to seal the demon back inside Muku, and Ryūzetsu gives her life in a technique that brings Naruto back. The box is dropped into the sea. In the end, the film reveals that Naruto's arrest was staged from the start.
No spoilersOpens once you mark the title as seen.