A little-known Tokyo-based company's commitment to biomass has made it a darling among investors.

As of the end of trade Wednesday, First Energy Service Co. had jumped 42 percent in the past month, making it the top performer on the Topix index, which lost 4.4 percent in the same period. First Energy jumped 8.8 percent on Thursday after the company's chief executive officer said he's eying more investment in power plants fueled by organic material.

Investors have flocked to First Energy as the company reiterated its commitment to woody biomass, increased its dividends and as an equity analyst highlighted the company's strong growth potential.