The rules of real ninjas

A new boy has joined the class, and he's brought a lot of trouble with him. He doesn't talk to anyone, swears, and gets into fights. His classmates soon realise that dealing with him won't be easy. But Ivoš doesn't have it easy either. Luckily, Lenka, a social worker who practices martial arts, is there to help. Thanks to her and a book about ninjas, Ivoš becomes a follower of the ancient warriors' art. He learns that problems aren't solved by running away or fighting. Will he finally be able to face them like a real ninja?