0524 GMT September 18, 2019
A spokesman for the firm confirmed it had raised around ¥2.65 trillion ($23.5 billion) via the unit's IPO, making it Japan's largest and the second-biggest globally after Alibaba went public in 2014, AFP reported.
But the stock opened at ¥1,463, significantly lower than the initial offer price of ¥1,500 per share, and headed lower from there.
The shares finished the session at ¥1,282, down 14.5 percent from the IPO price with heavy selling into the close.
Analysts said the IPO had not come at a particularly good time for the new company, named SoftBank Corp., as global markets have been suffering in recent months and Japan is taking aim at what they see as mobile operators' overly high prices.
The benchmark Nikkei 225 index slipped 0.6 percent while the broader Topix index was down 0.4 percent.
Other market players said tepid demand was not helped by an embarrassing episode earlier this month when a technical glitch left tens of millions of SoftBank and UK mobile phone operator O2 customers unable to access data.
"The number of those who wanted to buy the shares was rather small", said Masayuki Toshida, senior market analyst at Rakuten Securities.
"Concerns that SoftBank's investment costs could rise because it would not be able to use Huawei parts is a reason not to buy the shares," said one analyst in Tokyo, who declined to be identified.
SoftBank took more than one-third of its mobile unit public and was able to sell the full offering of 1.76 billion shares at the IPO price of ¥1,500, beating the previous national records set by Nippon Telegraph and Telephone (NTT) — a Japanese telecommunications company headquartered in Tokyo — in 1987 and its subsidiary NTT Docomo — the predominant mobile phone operator in Japan — in 1998.
The blockbuster IPO is seen as part of boss Masayoshi Son's strategy of transforming SoftBank from a Japan-based telecom company to a global hi-tech investment firm.
Son has already said the IPO would go towards swelling the coffers of his SoftBank Vision Fund, which is worth an estimated $100 billion and has taken stakes in some of the hottest tech firms, including Uber, Slack, WeWork and Nvidia.
Analysts at S&P Ratings have said the IPO "would further underline SoftBank's transition to an investment holding company".
Another ratings agency, Moody's, said the IPO would ‘enhance transparency’ in the parent company's investment portfolio because the mobile unit's "share price and daily market value will be available to the public".
The SoftBank parent company itself has said the listing would give the mobile unit "greater managerial autonomy to develop its own growth strategy".
It has also said the listing would help clarify the roles of the parent company and its mobile unit.
The mobile unit said in a statement alongside the market debut that it expects net profit of ¥420 billion on sales of ¥3.7 trillion for the full year to March 2019.
In the year that ended March, it has logged net profit of ¥400.75 billion on sales of ¥3.58 trillion, it said.