Jesper Koll is leaving JPMorgan Chase & Co. after running the firm's equity-research team in Tokyo for more than five years.

Koll resigned at the end of March to pursue a "new career opportunity," he wrote in an internal memo obtained by Bloomberg, without giving more details. JPMorgan's management team is working on the transition, Koll said in the memo. Yukako Yoshino, a spokeswoman for the bank, declined to comment.

JPMorgan hired Koll, 54, to head its Japanese stock strategy team in November 2009. The former chief economist at Merrill Lynch & Co. and hedge-fund manager is known for his enthusiasm for Japan and its equity market, a view that's become more common since 2012 as the Topix index rallied 87 percent under Prime Minister Shinzo Abe.