After CEO resigns over drug allegation, Olympus shares plummet by more than 5%.

• On Monday, Olympus Corp's shares dropped after the company's CEO resigned due to a drug allegation.
• An allegation was made against Stefan Kaufmann, a German national, that he bought illegal drugs, according to a notice from Olympus.
• The company, in collaboration with legal counsel, promptly examined the facts, submitted a report to the investigative authorities, and fully cooperated with their investigation, according to a statement.

On Monday, the company's chief executive officer resigned due to a drug allegation, which caused him to fall.

Following the resignation of Stefan Kaufmann, the stock on the Tokyo Stock Exchange slid 5.3%. Despite this, Olympus shares have outperformed Japan's benchmark Nikkei 225, rising 31.9% so far this year.

An allegation was made that the German national bought illegal drugs, according to a notice from Olympus.

The company, in collaboration with legal counsel, promptly examined the facts, submitted a report to the investigative authorities, and fully cooperated with their investigation, according to a statement.

"The Board of Directors concluded, after investigating the matter, that Mr. Stefan Kaufmann's behavior was likely incompatible with our global code of conduct, core values, and corporate culture."

In April, Kaufmann, 56, who had worked at Olympus for two decades, took over as CEO and led efforts to expand the company's medical equipment division. He complied with a request to offer his resignation, the company added.

As Kaufmann's replacement is being considered, Takeuchi will resume his CEO duties.

CNBC was unable to reach Kaufmann for comment.

Over the years, Olympus' leaders have faced controversy, including the 2011 scandal where the company admitted to using fraudulent accounting practices to hide losses on investments. This was exposed by whistleblower Michael Woodford, a former CEO, and led to several former executives pleading guilty to falsifying accounts.

Japan's strict drug laws have endangered the careers of several foreign executives, including a Toyota Motor executive from the US who resigned in 2015 after being arrested and released on suspicion of importing oxycodone illegally.