Tokyo Metro Co. shares debuted on the Tokyo Stock Exchange on Wednesday in what would be Japan’s biggest initial public offering in six years. But shares of Asia’s oldest subway operator were untraded as of 9:50 a.m. after drawing massive buy orders. The offer price of 1,200 yen ($7.9) per share places the market capitalization of the country’s second biggest railway company by passenger volume at 697.2 billion yen on the TSE’s top-tier Prime Market. The subway operator raised 348.6 billion yen in the IPO, with the central government and the Tokyo government selling half of their respective ho…