Shares in Olympus corporation surged 23% on Thursday, a day after the company's chairman Tsuyoshi Kikukawa resigned.
Mr Kikukawa's resignation came amid a controversy over $687m (£423m) fee paid to financial advisors for acquiring a British company: Gyrus.
The fee came into focus as former chief executive Michael Woodford claimed he was fired for questioning the payments.
Olympus' shares fell more than 50% after Mr Woodford was sacked.
However, analysts said despite Mr Kikukawa's resignation, the company still needed to answer key questions about the payments.
"The company's problems were matters of disclosure and corporate governance, so even after it said it has revealed everything, I don't think anyone was convinced that it has and questions remain," said Fujio Ando of Chibagin Asset Management.
Olympus acquired Gyrus for $2bn. Advisory accounted for almost 36% of that amount, a high proportion compared with the industry norm of 1% to 5%.
The company has maintained there was nothing wrong with the payments, but has said it will launch a third-party investigation into the matter.
Analysts said share prices would not rebound until the company gives a satisfactory explanation about the payments.
"This is short covering following the steep drop. [Investors] are not buying because of what the company said," said Mitsushige Akino of Ichiyoshi Investment Management.
"Share prices won't return to their appropriate market price level until a thorough report by a third party is issued."