The Neighbor No. Thirteen  (2005)

Theatrical Release Information:
The Neighbor No. Thirteen

After suffering years of abuse by his sadistic classmates, a vengeful Japanese boy develops a murderous alter ego in order to better deal with his traumatic past in director Yasuo Inoue's shockingly violent feature debut. As a high school student, shy Juzo was forced to endure the humiliation heaped upon him by the abusive Akai. Years later, when Juzo is hired to work at the same company where Akai is employed, he moves into the apartment directly above his former tormentor. As Juzo's revenge-minded alter ego slowly begins to eclipse his quieter, more withdrawn public persona, the people who have wronged him in the past begin to fall one-by-one to a mysterious psychopath. ~ Jason Buchanan, All Movie Guide