SoftBank Group Corp.’s 2.65 trillion yen ($23.5 billion) initial public offering for its telecom unit was fully subscribed, including an extra allotment of shares, people familiar with the matter said.

The underwriters were able to cover their entire book by Wednesday, thanks to strong demand from retail investors in Japan and overseas buyers, said the people, who asked not to be identified because the information isn’t public. Brokers are collecting more orders from individual investors, which will probably push the stock above the preliminary price of 1,500 yen apiece when trading begins on Dec. 19, they said.

Including an overallotment of about 160 million shares, SoftBank is selling a total of roughly 1.76 billion shares in the telecoms business. Representatives of SoftBank and the lead underwriters declined to comment on the book-building process.

The shares of SoftBank fell 4.9 percent in Tokyo on Thursday, after reversing a steeper decline following the news that the IPO was fully subscribed. A mobile service outage in the afternoon didn’t appear have a significant impact.

SoftBank is set to announce the final offering price on Monday. The figure is unlikely to change, even amid a global stock sell-off that’s dragged the Nikkei 225 Stock Average down for three straight sessions this week. That’s because additional demand for the stock may also come from institutional investors, who will be purchasing shares to include in their portfolios. SoftBank and its bankers also embarked on a marketing campaign to attract retail investors.

Koji Owada, 55, is one of those. He visited a branch at Nomura Securities Co. on Wednesday afternoon to open a brokerage account in order to buy 100 shares of SoftBank Corp., the name of the telecommunications unit being listed. Owada, who works in the service sector and lives in Tokyo, said he made a loss when he bought shares in Nippon Telegraph & Telephone Corp.’s IPO in 1987. He said he’s now a SoftBank wireless service customer.

“SoftBank is well-known and president Masayoshi Son is a good guy, which reassures me,” Owada said. “No matter how well a business is performing, and even if it’s a low risk, you don’t want to buy shares in a company that you know nothing about.”

SoftBank’s telecommunications arm is a cash-generating business, which spans wireless, broadband and fixed-line services and has 34 million mobile subscribers. The Japanese billionaire is transforming his Tokyo-based company from a telecom operator into a global tech investor, but the listing comes at a time when Japan’s wireless industry has come under pressure from the government to reduce phone bills. The entry of e-commerce giant Rakuten Inc. is also raising the risks of a price war next year.

Nomura Holdings Inc., Goldman Sachs Group Inc., Deutsche Bank AG, Mizuho Financial Group Inc., JPMorgan Chase & Co. and Sumitomo Mitsui Financial Group Inc. are the joint global coordinators.

SoftBank says it’s targeting a dividend payout ratio of about 85 percent of net income for the new company. Based on SoftBank’s net income in the last fiscal year, investors who buy at the preliminary IPO price would get a dividend yield of almost 5 percent.

“This is money I’ve been saving bit-by-bit in my bank account, so I don’t want to lose any money,” Owada said. “The high dividend payout is attractive, but if the stock rises on the first day, I plan to sell.”