The problem with Tokyo Metro is that it might just be too much of a railroad, some analysts argue.

Shares in the subway company started trading on the Tokyo Stock Exchange on Wednesday following the biggest initial public offering in Japan in more than half a decade. A total of ¥348.6 billion ($2.3 billion) was raised, valuing Tokyo Metro at about ¥700 billion.

Public enthusiasm has been strong for the listing and for the company itself, which began as the Tokyo Underground Railway with a pilot service that covered a 2.2-kilometer stretch between Asakusa and Ueno in 1927.