Black Rat (2010)

After receiving a chilling email from Asuka, a classmate presumed dead by suicide, six friends are drawn together for a late-night reunion. Their anticipation quickly turns to terror when they find themselves targeted by a mysterious figure donning a rat mask. As the night unfolds, the group grapples with the horrifying realization that they are caught in a deadly game of revenge, forcing them to confront their past and uncover the truth behind Asuka's tragic fate. Tensions rise as they fight to survive against an unknown enemy.