Soaplands are simply Japan's answer to a western whore house. They came to existence after the laws of when explicit full service prostitution was outlawed in the country.
To skirt these laws the operators changed their ways and continued operating their existing brothels as bath houses which still exist to this day. Permits allowing Soaplands to operate are no longer issued and can only be bought out by existing permit holders. In the early decades of its existence many Soaplands went out of business over night as the permits were only valid if the person responsible was still alive.
This resulted in many owners transferring their licenses to operate to a dummy company so the fate of the establishment wouldn't be on the shoulders of one individual. As the buildings of these brothels operate in cannot be rebuilt or have any form of structural renovations done that alter the original floor plan they are mostly structurally questionable.
Most Japanese buildings are demolished and rebuilt regularly to conform with the latest building regulations that protect them from major earth quakes. Many of the touch ups you see today are simply band aid cosmetic fixes to the building. Retiling of the exterior with shiny new material is a commonly done renovation to attract the attention of passerby's.
As you can see by the picture linked the brothel has been designed to look like a Edo period castle. The three most notable Soapland districts in the Tokyo's vicinity are Yoshiwara, Kawasaki and Oomiya. Many operators in these districts start off with one brothel and slowly eat up their competitor as old generation operators struggle to compete with new tech savvy owners.
