SBI's unsolicited bid has met opposition from Shinsei's management, but the bank last month cancelled plans to introduce a poison pill defence aimed at blocking the bid.
The holding company plan will be pursued after SBI ends its $1.1 billion tender offer to raise its stake in the mid-sized lender to 48% from about 20%. The offer is due to close on Friday.
The Nikkei, citing unnamed sources, said the online financial conglomerate is likely to raise its stake to at least 40% with its latest bid.
A spokesperson for SBI declined to comment.
SBI would need regulatory approval to become a bank holding company with a majority stake in Shinsei.
The company plan to boost its stake further after the tender offer has been flagged previously, but it has not previously given a specific timeline.
(Reporting by Sakura Murakami and Makiko YamazakiEditing by David Goodman)