SoftBank Group Corp.'s ¥2.4 trillion ($21 billion) initial public offering for its Japanese telecommunications unit has successfully secured sales for the bulk of its shares to individual investors, sources have said.

The lead underwriters, which had set a target of about ¥2 trillion worth of retail sales, have received enough reservations at around the indicated price of ¥1,500, said the people, who asked not to be identified because the information isn't public.

One brokerage completed half of its volume at a retail branch on the first day, they said.