Tokyo Portcity Takeshiba's biggest tenant will be SoftBank unit SoftBank Corp , whose Chief Executive Ken Miyauchi told reporters at the unveiling that 60% to 70% of the wireless carrier's employees are currently working remotely.

Excess space can be opened up to other group companies, Miyauchi said. Some of these are currently renting space around Tokyo from office sharing firm WeWork, which SoftBank has taken control of globally following a series of missteps at the U.S. startup.

The new development employs technology that supports social distancing, such as real time data on congestion at restaurants and SoftBank-developed robots for cleaning floors and making deliveries.

It also employs WeWork-style features like hot-desking, communal lounges and internal staircases that since the pandemic have raised infection concerns.

The move comes as group Chief Executive Masayoshi Son is loosening ties with the wireless carrier, with the group's stake in SoftBank Corp set to fall as low as 40%.

The sell-down of such core assets is funding SoftBank's bets on listed tech stocks, which have fuelled concern among investors about the group's opaque investing practices and sent its share price tumbling this week.

By Sam Nussey