A Google search confirmed my suspicion: I was staying in Kamagasaki — Japan’s biggest slum.

There were warning signs. The hostel I’d booked was ludicrously cheap. 1,000 yen for my own private room. You’d pay more in Thailand.

The hostel reception was extremely run-down and full of old men smoking. The receptionist took my money without checking my passport and then shoved me into the elevator with my room key. The ancient elevator struggled up the six floors, I doubted that it had ever been serviced.

I exited the elevator into a dark corridor that stank of cigarettes. Ominously, a sign showed a man smoking and falling asleep while a fire started. I couldn’t read the Japanese, but the message was clear. Well, I thought, this old place hasn’t burned down yet, what are the chances it happens while I’m here?

The final surprise came when I reached my room. It was the size of a single-bed, yet there was no bed inside. I had to sleep on the floor with just a duvet for comfort. The only other amenity was an ashtray. I squeezed inside, unable to turn around with my backpack on.

How had I ended up here, I asked myself? Turns out that Japan’s biggest slum is also one of its biggest secrets.

Japan’s biggest slum

Kamagasaki is its name, but you won’t find it on any maps. Japanese officials changed the name in the 1960s after a series of riots. This bureaucratic attempt was supposed to fix Kamagasaki’s crime-infested reputation.

Now called Airin-chiku, Kamagasaki is home to 25,000 day-labourers, a large percentage which are homeless. Most are elderly, and wake each morning in the hope of getting a day’s work on Osaka’s construction sites. Kamagasaki is crammed full of cheap hostels called doya, which cater to this poor population. The unlucky ones who don’t earn money that day either sleep in homeless shelters or on the streets.

The area around my hostel was packed with old men. All were shabbily dressed, in haphazard arrays of suit-jackets and trackpants. They loitered aimlessly, talking and smoking. Some waited on the street corners, trying to sell old car batteries, individual packets of instant noodles and TV remotes. This was a thieves’ market and everyone looked in poor health — In Kamagasaki the tuberculosis rate is 40 times the national average.

This concentration of marginalised people has made Kamagasaki an infamous hideout for fugitives. High profile murderers and rebels have evaded the police by staying here. With its myriad alleyways and legions of unidentified workers, Kamagasaki’s an easy place to get lost in.

It’s no surprise then that Kamagasaki is also home to Osaka’s oldest red-light district. To reach it, you must pass Yakuza offices with glitzy cars parked outside. The girls sit in windows, Amsterdam-style, while old women usher customers in.

Prostitutes aside, Japan’s biggest slum is a man’s world. It felt post-apocalyptic being somewhere with no women and children around. My hostel only had a shared shower, like in a prison. Outside, men drank beer and grilled cheap meat by the road. One night a fight erupted and a battalion of policemen descended. In a place known for police brutality and ensuing riots, the atmosphere was electric.

I escaped the tension by returning to my room. I lay on the wooden floor and tried to sleep. Through the thin walls I could hear my neighbour breathing in the next room. I couldn’t help wondering whether he was a murderer, hiding from the authorities here.

Yet despite all this, Japan’s biggest slum still felt safer than any other city I’d visited in the world.