Align Partners' stake in SM, a pioneer in K-pop behind acts like Girls' Generation and Red Velvet, is just 1% - but still worth tens of millions of dollars.
HYBE hasn't disclosed whether it intends to buy more of SM after the current tender offer.
Taken together, the 40% stake would cost HYBE about 1.137 trillion won ($884 million) under current plans - though SM shares traded above HYBE's tender offer price on Thursday.
Align's Lee said this would become a proxy fight, with SM's current executives wooing shareholders with plans to improve SM's sales and profitability.
($1 = 1,284.9500 won)Reporting by Hyunsu Yim and Joyce Lee; Editing by Kenneth MaxwellOur Standards: The Thomson Reuters Trust Principles.