Sago, a Goldman Sachs alumnus and former chief investment officer of Japan Post Bank Co where he was one of "Seven Samurai" who engineered a more aggressive investing approach, took the newly created strategy job at SoftBank in 2018.

The departure of one of CEO Masayoshi Son's key lieutenants comes after power consolidated around Vision Fund chief Rajeev Misra and Chief Operating Officer Marcelo Claure, and as SoftBank invests in public companies under rising star Akshay Naheta.

Sago "played a crucial part in expanding SBG's potential as an investment company," Son said in a statement, which did not provide a reason for the departure.

Last year, following investor pressure to improve oversight at the group, SoftBank removed several high-profile executives from the board, including Sago, Misra and Claure.

SoftBank Group last month reported that third-quarter net profit ballooned more than 20 times thanks to recovery at its Vision Fund.

(This story refiles to correct capitalisation in para 2 and 3)

(Reporting by Ritsuko Ando and Sam Nussey; Editing by Kirsten Donovan, Jason Neely and David Goodman)