Sasano Nomura, 26, mournfully recalled the first time she put dogs to sleep as a staffer at the Small Animal Management Center in Kochi Prefecture, saying: "I killed them."

Nomura, who began working at the center six years ago, still feels depressed when she hears dogs and cats suffer in the gas chamber.

The center is situated in a coastal town near the city of Kochi and manages thousands of dogs and cats dropped off for various reasons. The main ones are that their owners no longer want them, can't keep them where they now live, or have grown too old to care for the animals.