Broadly speaking, public bathing facilities in Japan fall into one of two categories: onsen and sento. While the onsen exist for the pleasure of relaxation and the health benefits of bathing in nutrient-rich water, the sento are local establishments which serve the far more practical need of daily hygiene. Indeed, the two kanji which make up the word sento (銭湯) mean “coin” and “hot water”. In other words, you are simply buying hot water heated from the water supply just like you would if you ran a bath at home.
Sento numbers grew significantly in the post-war era as the population exploded. Cities became more densely packed, houses got smaller, and many families bathed at their local sento as not all homes had a bathtub. During their heyday in the mid 1960s statistics suggest that there were well over 20,000 sento throughout the country. Obviously times have changed and today they number less than 5,000 with maybe 500-600 in Tokyo, but they are still a fairly common sight in the residential areas and provide a unique opportunity to peek into another aspect of Japanese culture. Entrance is typically about ¥500 but sometimes you need to bring your own shampoo and body wash.
Into this mix of onsen and sento you also have the super sento (suupaa sento). Bathing houses that offer a wide variety of bathtubs, saunas, and other services, but do not use the natural water that would otherwise give them the status of onsen. Edoyu in Ryogoku, for example, is as refined and elegant as any other public bathing establishment, and at ¥2,380 is among the most expensive. But is, technically, a super sento, as unfitting as this might seem.