Given the meager production values, middling music, broadly forthright writing and direction, and near total lack of credits, 'The roommate' immediately comes across as a very indie, low-budget feature. One is readily reminded of any other movie one may have watched that is built on little more than passion and a camera. That said, this is almost certainly more ham-handed than comparable flicks. None of this is an inherent mark against the film, but a viewer must be prepared to engage with it for what it is.
In every sense this is scarcely above the level of "home movie." Sound effects, for example, are clearly derived from the most rudimentary components, including more than one instance of manipulation in one way or another of a balloon. Still, there's something admirable about such ingenuity - perhaps more so in light off the dearth of other aspects to be especially praiseworthy. 'The roommate' is an unmistakable effort to produce a horror flick about a malevolent entity, the sort like 'Ringu' or 'Ju-on' that proliferated in Japanese cinema in the late 90s and 00s - except, pointedly to the most modest standard. I admire that endeavor, but there's also a distinct lack of thrills, tension, or basic atmosphere that means the film just trundles along without having any real impact.
I'll say this much - I like the cast. I think they do well to inhabit their characters, arguably exceeding the material with demonstration of nuance of expression that I appreciate. Against all odds, despite the bare simplicity of the title, filmmaker Hisaaki Nagaoka does arrange a few moments that I think are done well. To my surprise and satisfaction, that includes the climax and denouement - a sequence that provides the single twist off the movie. And even with the limitations 'The roommate' bears as a whole, the last stretch is written and realized pretty well.
To be frank, there's little reason to watch this, and definitely no reason to seek it out. It's difficult to become invested in given the nature of the film, and more so for minimal plot, let alone plot progression. Yet there's something to be said for trying one's hand at such a feature with so few apparent resources, and more than that, the acting and the finale at least save the whole affair from completely sliding into the memory hole of cinema.
If you happen to come across this, then it's not the worst way you could pass your time. Just be prepared for a very amateurish construction, keep your expectations in check, and by no means go out of your way to find it. If nothing I've written has dissuaded you - 'The roommate' is mildly entertaining. And I suppose sometimes that's enough.