Tokyo Metro shares soared more than 40 percent on their debut on Wednesday after its government owners raised US$2.3 billion in Japan's biggest initial public offering since 2018.

In early trade Tokyo Metro shares were at 1,745 yen (US$11.5), up 45 percent from their issue price of 1,200 yen, with reports saying the issue was 15 times oversubscribed among investors.

Proceeds from the IPO will redeem reconstruction bonds issued after the 2011 earthquake, tsunami and nuclear disaster in northeast Japan that killed 18,000 people.

The listing reduces government ownership, split between the country and Tokyo city, to around 50 percent. Many Japanese rail operators are already privatised.

To attract investors, perks for buying more than 200 shares included tickets to the Tokyo Metro museum and golf range, as well as free tempura toppings at its noodle stands.

The IPO is Japan's largest since tycoon Masayoshi Son's tech and telecoms conglomerate SoftBank Group raised a national record of US$23.5 billion by listing its mobile unit in 2018.

London built the first public underground railway, but in 1927 Tokyo became the first Asian city with a subway.

Each day around 6.5 million people ride the Metro's nine lines, which are part of a vast transport network serving the capital and its sprawling suburbs.

Four other subway lines are run separately by the Tokyo government, alongside private services and East Japan Railway's overground routes such as the Yamanote Line.

The network's cleanliness and efficiency contrasts with the often creaking infrastructure of other big cities like London, Paris and New York, where many operators are deep in debt.

Tokyo Metro posted a net profit of 46.3 billion yen for the fiscal year that ended in March 2024, up 67 percent from a year earlier. This year it is aiming to increase this to 52.3 billion yen. (AFP)