Ranjan Pai, the billionaire chairman of Manipal Education and Medical Group, has become the largest shareholder in Byju's Aakash Education Services Ltd. Pai has acquired a roughly 40% stake for about Rs 2,495 crore, or $300 million, pegging Aakash's valuation in the range of $750-800 million, a notch below its near $1 billion sale to Byju's.