Bain Capital plans to make a bid to buy shares of software company Fuji Soft without support from the company’s board of directors, kicking off a rare hostile bid in Japan against KKR.

The Boston-based investment firm disclosed the plans in a presentation Wednesday after Fuji Soft’s board rejected a higher offer from Bain in favor of going private with KKR. Bain said it had "strong concerns” about Fuji Soft’s process to go private, and decided to proceed with its bid without the support of the company’s board.

Last week, Bain said it planned to pay ¥9,600 a share for Fuji Soft — 1.6% higher than KKR’s offer of ¥9,451 and valuing the company at around ¥647 billion ($4.2 billion).