TOKYO, April 4 (Reuters) - Hong Kong-based activist investor Oasis Management said on Thursday it would start a campaign against Japanese cosmetics and skincare firm Kao Corp , demanding that the company cut underperforming brands.

"If Kao focused on its cosmetics and health & beauty segments and improved marketing, Oasis believes its stock price would exceed 10,000 yen per share, a 76% upside from current levels," the hedge fund investor said in a statement. (Reporting by Makiko Yamazaki; Editing by Sandra Maler)