I've cut back on the renting of Asian thrillers and horror movies recently after a bad run of them, but I picked this one off Blockbuster's shelves on impulse and while it's no masterpiece I'm rather glad I did because it's really not bad at all.
A Hong Kong thriller derived in part from the old urban legend about someone who wakes up in a bath of ice and discovers that (at least) one of their kidneys has been swiped, Koma starts off with such a discovery in a hotel where the perpetrator might have been witnessed by our heroine (Ching) attending a wedding. But it may be that she's only identifying the suspect (Ling) because Ling's been sleeping with Ching's boyfriend. After initial hostility a kind of friendship develops between the two women - but the real kidney thief is still out there and killing, and even Ching isn't safe despite having kidney problems of her own....
Generally quite exciting and engrossing although it tried to have one plot twist too many at the end and the finale is a bit implausible, but overall it's nicely done. It's also quite short, coming in at a tight 85 minutes or so. Pleasantly nasty and I can even see a US remake being fairly effective if the right talents get assigned to it. Worth a look.