Gô Shibata’s “Late Bloomer,” which opens Friday at the Pioneer Theater, is a curious story of a serial killer who is severely disabled. The film initially seems like a documentary because the protagonist has the same name as the actor who plays him, Masakiyo Sumida. Although the film leaves Sumida’s ailment unexplained, it depicts him getting around in a motorized wheelchair and communicating through a keyboard-operated speech aid. The film documents his laborious daily routines, heavy beer consumption, and fondness for gum-ball machines, but it soon unmasks itself as a fictional construct when Sumida develops a hopeless crush on his caregiver Nobuko (Mari Torii), a college student researching for a paper.

“Late Bloomer” is a huge departure from the atmospheric, supernatural material prevalent in the Japanese horror genre. This black-and-white film is a unique hybrid of realism and hyper-stylization that aptly illustrates the delirium of murderous rage. It also delves deep into the psychological state of a lonely outcast in a way that recalls “Taxi Driver” and “I Stand Alone.” Mr. Shibata isn’t manipulating the audience with easy guilt trips. Instead, he presents an uncompromising portrait of a human being numbing his alienation and pain with alcohol and pornography.

The blood begins to spill when Nobuko fails to return Mr. Sumida’s affections. He unleashes his pent-up anger by indiscriminately taking lives. Although the film’s depiction of the disabled isn’t exactly flattering, it forces able-bodied people to re-evaluate our attitudes and prejudices toward the handicapped. While its digital video aesthetic probably has consigned the film to the festival circuit, it will reward moviegoers who find it and give it a chance. — Martin Tsai