The Samurai Kids are ready to travel back from China to the Cockroach Ryu, nestled in Japan’s Tateyama Mountains. But then the unthinkable happens: Kyoko, one of the Cockroaches, is kidnapped. Sensei knows it is the mark of his old enemy Lu Zeng, an evil minister of the Forbidden City who is obsessed with eternal life. The Cockroaches must make a perilous journey to the Forbidden City, during which they encounter the mysterious, forest-dwelling Lin people. But Niya, the boy with one leg, has his trust tested when he learns that his best friend, Yoshi, is keeping secrets. Even worse, it seems that Sensei is not revealing all he knows either. Will all these secrets keep the Cockroaches from achieving their most important mission yet rescuing Kyoko before Lu Zeng performs horrible experiments on her?