But in the same markets sit the cats and kittens. If anything they face a worse fate than the dogs.
"Cats are placed into boiling water while they are still alive," an RSPCA representative told us. "They are basically boiled to death over a long period - under pressure - they are using pressure cookers." They call it cat juice.
"They are put into these large steel vats and boiled down over a long process. The water is then run off into a kind of tonic - it is mixed with herbs and bottled and sold as a kind of elixir. It is supposed to promote good health, specifically targeting arthritis."
Having been physically threatened in the market, I now had to depend on animal campaigner Mr Yang with our secret camera. We wanted to know what happened to a female cat we filmed - she had two kittens snuggled by her side. We were not prepared for what Mr Yang would come back with.
He soon discovered that the mother was already juiced. And then, a squeaking noise. And we found her last surviving kitten just one stage from the pot - alone and crying amid the roar of the gas flames. We paid the butcher, and saved her life.
The Korean government admits there are no medical benefits to cat juice, but cruelty laws are left crying out to be enforced.
There are a lot of cats around the world called Lucky, but this one really is, as every other cat in that market will soon be dead. By night the kitten still refuses any food.
It took all this effort for one tiny survivor, but animal rights activists have to count even the smallest victory. They are few and far between in a country that considers cats to be evil.
One lone man runs a refuge willing to take Lucky. His home is overrun by over 160 cats and dogs, but he can no longer allow them to go to new homes after some wound up eaten by their new owners.
"We love them and somebody must do the decent thing," he says. Lucky is meanwhile taken in by one of Seoul's few animal welfare activists. For this little kitten, it is a safe house in enemy territory.
For the RSPCA, the trip has confirmed the worst - not just the cat juicing, but cat furs are now arriving in Europe from nations across Asia. The products give no warning that you are wearing cat.
"We would ask people to write respectfully and as objectively as they can to press the Korean government to implement its own animal protection laws and to extend protection to the cats and dogs that we have seen."
Telephone number for WSPA, World Society for the Protection of Animals:
020-7793-0540 (United Kingdom)
Lucky is finally accepting milk from a bottle.
