During the Allied occupation of Japan following World War II, many members of the Japanese peerage lost their titles and were subject to crippling taxation on their real estate holdings.

Yasujirō Tsutsumi, who controlled the Seibu Railway through the Kokudo Corporation, arranged to buy several of these families' properties at a discount and used them to develop hotels.

The Tokyo Prince Hotel opened in 1964 on a site that originally housed graves of several Tokugawa family shoguns, whose bodies were moved to the neighboring temple of Zojo-ji.

Tsutsumi registered Seibu Railway shares owned by Kokudo in the names of various affiliated individuals, often without their permission, so that the true ownership of the company was not readily apparent.

His holdings in Kokudo and Seibu led to his being deemed the "world's richest man" by Forbes magazine for four consecutive years from 1987 to 1990, with estimated net worth of $15–20 billion during the height of the Japanese asset bubble.

[4] As of June 2013[update], Yoshiaki Tsutsumi remains a major investor in Seibu Holdings through his 36% investment in NW Corporation, the second-largest shareholder in the company with a share of around 15%.