This is a film based off the novel by Koushun Takami, which has been translated into English. To get this film, you can purchase this online or look for a subbed version that may be streaming online. That is how I found it.
It's about a game for which an entire ninth grade class is kidnapped, and put on an island reserved just for the game, a year to participate in. The object of the game? Be the only one to survive. You must kill the other students so you can get off the island as a hero. You are equipped with survival supplies and a weapon. If you refuse to play, your collar explodes and you die.
If you value your life, play. Kill. Destroy.
I absolutely love this movie. The bloody plot makes me excited. The movie is not made all that well. The killings are extremely fake like in a bad horror movie. Squirts of blood and other things just to tell you that they died more than tell you how they died. Compared to the manga, which is more stricly based on the novel, this is less gory (believe it or not) and portrays the person in charge as a pitiful old man who seems to hate the game just as much as the children have.
This movie is actually really entertaining, if not sick, and even though it lacks a few things, it is something I'd watch again.