Source: http://imdb.com/title/tt0434179/

"...In Marebito, ...Tsukamoto plays Masuoka, an amateur videographer who becomes obsessed with peoples fear and capturing it on video...
With his video camera in hand, Masuoka begins his journey into the subterranean regions of Tokyo.
While traveling through the creepy tunnels and pathways, Masuoka learns of DEROs, or, Detrimental Robots, that roam the underground and feed on the blood of the living..."