TOKYO—The Tokyo Stock Exchange inaugurated its new top-tier Prime section on Monday, and all the familiar names were present, Toyota, Sony, Honda and the like.

And then there was Econach Holdings Co. , which has 13 full-time employees and hasn’t paid a dividend since 1969. The company owns Thermae-yu, a bath and spa in a Tokyo red-light district that features a massage parlor, a pub and all-night service.

It is no insult to say that Econach operates at some distance from the stock exchange’s aim that Prime companies “center their business on constructive dialogue with global investors” and serve as “investment instruments for many institutional investors.” The bathhouse’s top-tier ranking can be chalked up, in part, to Japan’s respect for the venerable, an area in which Econach excels. Its history dates to 1926.