Some of the world’s biggest energy traders are looking to get ahead in Japan’s nascent power market.

From Royal Dutch Shell PLC to German utility RWE AG, companies are hiring, reassigning staff and building relationships with Japanese firms to profit in the $136 billion market. After building mature markets in Europe and the U.S., they have their sights on the third-biggest economy, which is taking shape the way European trading did 20 years ago.

While western markets are increasingly dominated by renewable energy and shrinking profit margins, the potential for price volatility and arbitrage in Japan are a trader’s dream: It has four distinct seasons, a growing supply of intermittent renewables, an uncertain future for its massive nuclear fleet and two separate grids, not to mention a heavy reliance on imports of natural gas, which many of the new entrants already trade.