SoftBank Group Corp. has tapped Nomura Holdings Inc. as lead manager for a domestic bond sale to raise as much as ¥400 billion in what could be one of the biggest in the Japanese corporate bond market, according to sources familiar with the matter.

The conglomerate is preparing to sell ¥300 billion to ¥400 billion of seven-year notes to individuals, and may set the bond's marketing range as early as this month, for issuance in September, according to the sources, who asked not to be identified because the matter hasn't been made public yet.

SoftBank, which last month unveiled plans for a second enormous technology fund, has a ¥400 billion bond due Sept. 12.