Question: What is the agency issue in accounting? Normally how the manager manipulate the share prices? 

Answer: Agency cost theory is in Finance, not in Accounting. It was the work of Jensen and Merckel two Stanford professors. Since managers are considered as Agents of the Stock holders, they pronounced that by giving them incentives for exemplary work done can motivate them to  perform better. Probably they didn't mean harm at that time but it lead to wide spread stock rigging and Accounting scandals which culminated in the debacle of Fortune 500 companies like Enron, World crossing etc;
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