Hanjin Group Chair Walter Cho is tightening his grip on Hanjin KAL, the holding company of Korean Air, with fresh share purchases just as its second-largest shareholder, Hoban Group, has notified regulators that it may now hold the top stake. In a regulatory filing Monday, Hanjin KAL disclosed that Cho had agreed to buy 325,000 of its shares for 37 billion won ($28 million) via block trade between Dec. 3 and Jan. 1, citing a goal to strengthen responsible management. Once complete, the deal will