Grotesque

A couple is on their first date, and while they are peacefully walking, they are attacked by a stranger who knocks them both out—this is how Grotesque begins.
Upon waking, they find themselves imprisoned in a large room.

Tetsuo (The Iron Man)

A businessman and his girlfriend are involved in a car accident where they run over a stranger.
After hiding the body, they return home, but from that moment on, the man who was driving starts experiencing visions, nightmares, and, most disturbingly, he begins to see metal parts gradually emerging from his own body.