In reply to Blue Straggler:
Hang on. I'll try to be concise.
The couple discuss the troubling incident by phone, he goes to shave and discovers a small, sharp bit of metal jutting out his cheek. This becomes very infected and in time he becomes semi-delerious.
The tube:
he sits next to a woman who becomes possesed by the boy they think (and may have; we don't know) they killed in the hit and run. Very disturbing. She chases and tries to kill him in an abandoned mensroom. He manages to kill her.
Later his infection spreads dramatically but takes the form of metal, not diseased flesh. Even his tackle which he accidentally kills his girlfriend with.
Her body is hidden in the bath then the boy possesses her corpse and she attacks him. The boy is gathering strength and has an accentuated desire for revenge.
He manifests bodily at last and pays a call on the man.
Then begins the chase through Japanese suburb streets leading to an abandoned steel mill and the climax.
It's anyone's guess why much of the events take place or what they mean. I suppose it's an indictment of industrialism and it's dehumanising effects.
That's about it mate.
btw.....
where'dja get those boots? that's just not right; most gals'd kill for an outfit like that. lol nutter