Activist funds are increasingly disrupting Japanese privatizations, pushing for better protection of minority investors and driving up share prices as their pressure leads to higher bids and counteroffers.

One recent example is Mandom, whose shares jumped 11% Tuesday after a report that KKR had floated an offer more than 10% above its management buyout bid. The move followed buying by investors linked to activist Yoshiaki Murakami, who took over 20% of the shares and argued the bid was too low. The stock is now about 90% above its pre-MBO level.

A similar dynamic played out last month at Soft99, where Effissimo Capital Management made a rival bid for the car products maker at a price 2.5 times the level before the MBO announcement ¡ª an offer that ultimately prevailed.