Simply put, DeathTube is Saw minus any of the smarts or suspense. The comparison may seem lazy and obvious but if the shoe fits...I'm not about to amputate the foot and attach a new one just so I can go shoe shopping again.
Inouye (Shoichi Matsuda) and his fiancée are in the process of planning their upcoming nuptials when an acquaintance brings a most alarming website to his attention. DeathTube may be fake but it certainly looks real. It shows people trapped in rooms attempting to solve puzzles before time runs out and they are murdered in a variety of gruesome ways. The whole time, a number of dispassionate webcams coldly relay these events to countless curious viewers like Inouye. One ill-advised nap later, Inouye wakes up in a room that looks sickeningly familiar. He is now an unwilling participant on DeathTube.
As his panic grows, Inouye realizes that he is not alone. There are seven other people trapped along with him. They don't seem to have anything in common other than the puzzles placed before them and the fate that awaits them in case of failure. The early challenges range from silly mental exercises to physical ones like obstacle courses. No matter how innocent the nature of a challenge, someone always dies at the end of it. Soon the challenges themselves devolve into mechanisms of cruelty disguised as moral dilemmas. While you or I may recognize the film's destination right from the outset, Inouye and his fellow travelers get there the hard way.
DeathTube is a Japanese entry into the 'Torturous Traps' subgenre of horror that has been thriving in recent years. To be fair, the film actually does tone down the gore quite a bit compared to its competition. Other than a drill to the noggin early in the film, the violence is generally kept off-screen. What is shown is fairly pedestrian in nature with multiple folks being poisoned or shot to death. There is a bit of ugly sexual violence towards one of the female characters but even that is largely suggested.
Since the film doesn't boast wall-to-wall graphic violence, it relies on the challenges and games played by the characters to generate excitement. Unfortunately this comes at the expense of the characters themselves. They start out as cardboard cutouts in peril and don't really get fleshed out over the course of the film. Most of them are lucky if they have one defining characteristic. This makes it quite difficult to identify with them on any level other than the superficial. Considering the film is practically two hours long, the stunted characters demonstrate how little of a premium director Yohei Fukuda places on them. Fukuda is completely focused on mentally and physically punishing the soon to be slaughtered lambs and his effort shows in this area. The film carries a suitably grungy look which contrasts nicely with the pure simplicity of the games that are being played.
One area where the film develops an identity of its own is in the humor department. Don't get me wrong. There isn't anything funny about a group of people being systematically killed but I give the film credit for gleefully looking on the perverse side of things. The Saw franchise has Jigsaw and DeathTube has...well, I won't spoil it but the film's mascot is both ridiculous and fitting in a uniquely Japanese way. At other points, a wry sensibility is revealed by the fact that viewers leave comments on the DeathTube website while the players are going through their ordeal. The comments are snide, mean and condescending which is not surprising given how folks tend to abuse the shroud of anonymity that the internet provides. Of course, the joke's on them since DeathTube is constantly on the look out for more participants...and they fit the bill.