Dawn is still an hour away, and the brown clay of the training area is dull and matte under the stark lights. The air carries the characteristic tang of sweat, musty earth and sweet hair pomade.
A couple of dozen prodigious young men, naked but for a diaper-like loincloth, go through their exercises. They raise one leg sideways high into the air. They crash it down again. And as foot stomps clay, they exhale volubly, giving the place a sound reminiscent of an old railway station, complete with a steam train impatient for departure.
Along with sushi and geisha, sumo wrestlers are one of the most readily recognised images of Japan, the glaring physical exception in a country that otherwise is partial to the neat and dainty.
And the place where every sumo wrestler learns his craft is a training hall like this one, Musashigawa, located - as are most other halls - within striking distance of the sumo stadium in Tokyo's Ryogoku district.
The sumo day starts early. I got to the training hall at 5.30am, shortly after practice had begun. The front door was shut and nobody was around, so I assumed that one simply marched right in. So, I did - and found myself in the training area, surrounded by semi-naked wrestlers. They eyed me with bewilderment until a young wrestler of about 16
politely showed me the way to the viewing area on the other side of the hallway.
Sumo training halls (sumo-beya), known as stables in English, operate as combined practice and living facilities. Despite the name, there is no horsing around. The coach barks out orders with the kind of voice you normally hear in yakuza films. Like the rest of sumo, the stable is a serious, unsmiling, feudal world.